So I was working on something and suddenly one of the videos just became nothing, and the thumbnail is a triangle with an exclamation point. It's a 0x87160139 error.

I swear I did not move, rename, or delete the file, and this happened long after I loaded the file and did stuff with it and it worked fine, until suddenly it didn't.

Why id this happen, and how can I fix it without redoing what I did with the video, if I can do that at all?