It doesn't have to be "completely" lost. If it doesn't build on the current version of the compiler, and the compiler that was originally used to build only runs on an OS version for which you can't buy the hardware any more, then it might as well be lost, even if you have it right there in front of you. I have stuff on my Mac right now (I keep migrating my home directory forwards from machine to machine) that I keep basically as a souvenir, I know perfectly well that while it built on a NeXT in 1998 it won't have a chance in hell of compiling now.