And now, the rest of the story...
That the FATE story is the original source of both Wilkins' and Edwards' versions of the David Lang mystery, there can be no doubt¹. But there appears to have been some form of outside editing done even before either of these two authors penned their versions.
Both authors' versions have details that agree and disagree with each other and the FATE account. For instance, the FATE account describes the grass circle as tall and yellow with a fifteen foot diameter... Edwards says it was short and yellow, but agrees with the diameter, while Wilkins says it was a twenty foot diameter, but agrees it was tall and yellow. In other places, Wilkins and Edwards both seem to be adding details with a distinctly similar pattern: the FATE article gives no date whatsoever for the children's visit to the circle, but both Wilkins and Edwards do... Wilkins stating it as August 1881, and Edwards calling it April 1881. Stranger still, both accounts omit the section of the story dealing with Spiritualism, as previously noted.
My initial assumption as I first ran across their two accounts was that either Edwards copied Wilkins, or Wilkins copied Edwards; but the nature of the differences are confusing. At this point, I'm assuming one of two things happened: either one did copy the other, but from memory rather than from print, thus making simple errors from mis-memorization², or both authors copied their stories from a third source that I have yet to find, which may have had more or less detail than the FATE account. At this point, I don't know which is more likely... but, in the end, it's all really beside the point. Why?
Some readers may be asking themselves the same question a few people started to ask when the FATE article was first published: why did Palmer wait twenty-three years to publish the story?³ At the time, however, even more people were impressed and inspired by the story than were questioning it... so it took a while before someone decided to check.
In October, 1976, Robert Forrest and Bob Rickard were perhaps the first people to both investigate the basic facts of the story and publish the results, which they did in the British magazine Fortean Times, issue #18. Unaware of the story's earlier origins in FATE magazine, Forrest set about investigating the facts as put forward in the books by Edwards and Wilkins, mentioned above, by checking with the public records of libraries in the Gallatin, Tennessee area. His enquiries garnered a reply from one Hershal G. Payne of the Public Library of Nashville and Davidson County, who had also been interested in the David Lang story and had already investigated it some.
Payne had personally checked census records and related materials at his library and had found no evidence for the existence of either David Lang or Judge Peck. He further corresponded with the librarian in charge of the Gallatin Public Library who, together with several other knowledgeble people in the area, attested to the story's fictitiousness. Payne also contacted the Sumner County historian, who stated that there was no evidence of the supposed Lang family farm in existence; Payne then confirmed this for himself by driving to the supposed location of the farm... it wasn't there. That the story was false was also the consensus opinion of all the newspaper and literary researchers in the area he talked to.
In the course of his investigation, Payne formed the opinion that the whole story had it's origins in a traveling salesman named Joe Mulhatten, who was legendary for telling amazing stories and lived in the area in the 1880's. Mulhatten participated in local lying contests; and Payne feels that the story of David Lang was one of his best.
In a postscript to the above findings, Rickard added that he had heard of the exstence of an earlier article on the David Lang disappearance in the July 1953 FATE -- the issue with Palmer's original telling of the story -- after he had typed up Forrest's research... but he had no way to get a copy of the magazine, so could not comment on it's contents. But it wasn't long before someone who could get a copy of the FATE article decided to do more investigating.
That someone was Robert Schadewald who, after reading both the Fortean Times' article and Palmer's FATE article realized that new information directly conflicted with the earlier story... simply put, if Lang had never existed, then how could his daughter have told Palmer the story? So Schadewald did the only obvious thing possible; he re-tested Palmer's physical evidence for the story, the handwriting samples and the affidavit.
The affidavit had no notary seal, and the notary's name was neither typed nor stamped on it, which is unusual... and the writing on it looked strangely familar. With the permission of Jerome Clark, then Associate Editor of FATE, a copy of the 1953 FATE article -- with its illustrations of the documents -- was sent to handwriting expert Ann B. Hooten of Minneapolis, a nationally known Examiner of Questioned Documents. The resulting five-page report came to one simple conclusion: the note on the flyleaf and the sample of automatic writing had been written by the same person... unfortunately, the same person had also written the signatures on the affidavit. All three documents were fake, the production of just one person; Stuart Palmer.
So in December, 1977, twenty-four years after the original FATE article about the David Lang mystery had been published and eighteen years after both Harold Wilkins and Frank Edwards re-published it in its more familiar form, FATE Magazine printed an article written by Schadewald entitled "David Lang vanishes... FOREVER"; it was an apology for and a retraction of the account of the dissappearance of David Lang apparently created by Stuart Palmer.
So the only real question left is, did Palmer fabricate the story entirely, or did it actually originate in the 1880's as a lie told by Joe Mulhatten? Mulhatten had become legendary in the Nashville, Tennessee, area before Payne did his research, and Payne never tried to verify that Mulhatten had actually told the story... or if he existed. In Secrets of the Supernatural, Joe Nickell brings this last point into question, noting that no evidence has been presented to prove Joe Mulhatten was anything more than a legend himself, likely based on stories about a very real person, one Joseph M. Mulholland who is described as "a traveling salesman of Washington, Pennsylvania, who wrote... in the 1880s and '90s and read his semiplausible yarns in many a serious publication..." In any case, it's not unlikely that, had Mulhatten or Mulholland not actually told the story of David Lang, the story would have been attributed to him at a later date anyway simply because it sounded like something he would have come up with. So some research will need to be done to see if Mulhatten or Mulholland was involved or not⁴; but neither needs to be, as there is a simplier answer available.
In Palmer's original 1953 FATE article, "Sarah" at one point states: "This story is a famous one now. Ambrose Bierce, the writer of stories, was one of the many visitors who came that month after Father went and he wrote several of his most famous works about our mystery, cloaking it under the guise of fiction." Palmer then adds, in a footnote to the account, that Ambrose Bierce wrote three stories based on the Lang event, which he published in a book called "Can Such Things Be?"; Palmer even quotes a theory from Bierce's book about what could be causing such disappeances [all three stories are from a very short section of Bierce's "Can Such Things Be?", and are re-printed in the NOTES following this article ⁵].
So it's clearly obvious that Palmer was well-aware of Bierce's stories about mysterious disappearances, one of which -- entitled "The Difficulty of Crossing a Field" -- was likely his model for the creation of the basic Lang story, and another -- "Charles Ashmore's Trail" -- likely the origin of the part of the story about the circle and Lang's voice. Ambrose Bierce didn't steal the story from the Langs; rather, Stuart Palmer stole the story from Bierce⁷.

Last Thoughts
Looking back, it's interesting to note that at least three different authors -- Frank Edwards, Harold Wilkins, and Nandor Fodor -- who all referenced the original Palmer story in the July 1953 FATE also all failed to mention the aspect of the David Lang story that involved Sarah contacting her parents through Spiritualism. If these authors didn't copy each other, and it seems unlikely they did, then why did all three choose to edit out the same part of the story? Here are three thoughts on the matter.
First possible reason: the story is more mysterious with no closure to it. In offering a solution, the story loses the emotional impact of a loved one being lost and it becomes less convenient for use as an example of various theories about fourth dimensions, UFOs, and fairy circles.
Second possible reason: Spiritualism, a popular topic previous too and during World War I and II, was no longer a popular topic, nor one to be caught talking about. By the late 1960's in America, Spiritualism as seen by the public eye was full of frauds and hoaxes; so the authors removed the part of the story that would also remove this unpopular association from it. (See also: Anomalies Article: Spiritualism)
Third possible reason: The section of the story about Sarah contacting her deceased parents is the only part of the story which offered any physical evidence, evidence which eventually spelled out doom for the account, as we have seen. Perhaps the section was neglected in an effort to divorce the story from the questionable evidence... this, of course, assumes that there were more than a few authors who knew the story was false when they took it from FATE Magazine in the first place.
In the end, we'll likely never know -- all three authors are dead, now. Strangely, though, the story itself isn't... since the 1976 Fortean Times article and the 1977 FATE article, the fact that the David Lang mystery is a falsehood has been mentioned many, many times in books -- more times than I've found it treated as a true story⁶ -- but it makes no real difference to it's longevity. In its singular endurance in the folklore of parapsychology, the Mystery of David Lang stands out as a shining example of one of the completely unverified "facts" that are, unfortunately, so commonly still passed on and theorized about by new authors. Be wary.