Along those lines....
I once heard about a paper that was presented at some conference titled something along the lines of, "My Goodness: It Still Runs?!". The topic was some sort of early version of Unix running on some ancient piece of hardware doing some sort of industrial control. When I heard about it, a notable part of the paper was a mention that it was believed they had removed all bugs from the implementation.
Not quite a lost version of Unix, but almost a lost+found version. Has anyone else heard of this paper? Perhaps it is apocryphal? I've always wanted to read it, but never found a copy "in the wild."
- Dan C.