I'm not adding this to the tracker because I have NO idea what causes it.
Sometimes, for a reason I don't know, the entire contents of an event sheet are replaced wholesale with another open event sheet. The event sheet being replaced was not selected when this happened. It's happened to me on a couple of different occasions. The most recent time was particularly annoying, as I didn't have a backup (stupid, I know) and I need to rewrite the sheet now.
Anyone else have this happen to them? Any idea what might be triggering it?