Lost project recovery

Students often lose their projects, e.g. by saving over them with the wrong project. Would be great if we had a system for letting them try to recover their work. I have done this manually in the past, by searching the source code, which is stored by hash on the server, and sending them links to the project. But it would be better to have a system that works for everyone, so students could use a recovery tool to provide information about their code and get it back.

The risk here is that students might get access to other students' code.

Ideas:

1. Require that they give enough unique words to isolate the program sufficiently; if there are too many programs, insist on more words.
2. Ask followups by asking students to identify more words used in the programs, and have enough redundancy that guessing won't work.
3. Keep IP addresses for code and prefer or restrict to results that geolocate to the same area. (Probably a bad idea)