This just happened: I could not find the quiz paper of a student that I know was in class during the quiz. It is possible that she did not turn it in so she could later blame me for "losing her test" and demanding that she has the opportunity to retake the quiz. If that happens, how should I respond? Normally, I have the students hand me the test paper as they exit, so I don't know how I missed collecting her's in that fashion.