Entire project/files disappeared for no apparent reason?

I'm working on a fairly long/big project, and everything seemingly disappeared while I was working on it for no apparent reason. The program didn't crash or anything; it all simply disappeared as if I hadn't even started. I had the window open when it happened; I literally saw everything just disappear.

Thankfully, I'd saved a copy yesterday, and I was able to recover that, so I only lost today's progress and not the whole thing. Even in the recovered version, though, all the files I imported are gone, yet they still show up in the timeline in the way I edited the,.

I'd like to make sure this doesn't happen again. Anyone have any idea why it might have done that?