1928, March 23: Toad Found Alive after 20 Years in Stone
On March 24, 1928, The Ottawa Citizen, newspaper of Ottawa, Canada, ran an article stating that on the previous day in Emerson, Ottawa, a toad had been discovered entombed within the stone of a hotel wall that was being torn down. The hotel had been built 20 years previously (in 1907), so it was assumed the toad had been in the wall that long. The toad was "shrunken" and dusty, and assumed at first to be dead... but when touched, it "moved with a healthy hop."
I have only the one newspaper account of this matter, so there's not much to go on. I'll keep an eye out for other mentions or articles that can either confirm or refute the story.