Images disappearing from Media Library

A client of mine is having a weird issue… He’s uploaded an image in the media library and it keeps disappearing on him… it happened once about a month ago, I told him to reupload because he must’ve deleted it, and now it seems to have happened again. Image stays there for at most a week, and then it’s gone again. Same exact image. No other image in his 119-strong (should be 120) media library is exhibiting such behavior.

Any idea why this would happen?