Posting out of sequence just to get this out there. I've previously suggested using myTexts for writing on your ipad, citing its excellent interface and features. Those benefits remain, but today I discovered an unfortunate downside - it also randomly deletes files. I encountered this bug twice today, and upon discussion, discovered that many people I know have encountered it as well.
If you have myTexts, consider just uninstalling it. For me, I've switched over to My Writing Nook, and am so far content. But I'm backing up more frequently too.