How to prove receipt/no receipt of work? Last term, I collected some important projects from about 200 students. When I returned all of the work the next week, one student claimed that they had submitted their work, but never received it back. A misplaced project was highly unlikely, as they were individually bound in a uniform, bright cover and carried in sealed bags, so I assigned the student a 0. Still, I would like to have proof of “no submit”, especially as my supervisor occasionally wants an explanation for failing grades. But not having something is not proof of never submitting. What method can I use in the future to prove that a student did not submit their work?
I doubt this will work with 200 students, but the first thing I do when I collect assignments is check to see whose assignment is missing, and send the relevant students a message via the class messaging system. This does two things:


if there was a slipup at either end, this catches it quickly. Most often, the student says that they're turning it in late (I have an automatic submit-late-and-get-deductions policy). 
By using the class messaging system, I'm on record as having asked the student about the missing assignment. If they complain a week later that they did turn it in, I can point to the message and ask why they didn't respond to it.