I'm in IT and I've repeatedly heard stories of a server that was left stuck in a space that had a wall built in front of it, and was only discovered years later when the wall was torn down.
This 2001 article from The Register gives an example of such a claim:
According to a report by Techweb it was only then that those campus techies realised they couldn't find the server. Attempts to follow network cabling to find the missing box led to the discovery that maintenance workers had sealed the server behind a wall.
In one variety of the story, a fan starts to squeak and someone punches a hole in the wall to discover it.
I'm skeptical due to the fact that heat that would build up in a wall would fry the server.
Has a server (or servers) been walled in and discovered, still running, years later?