I know this is really old, but I just had the same thing happen! I never lose files and am careful to back up, but in this case, it just didn’t work out. I can’t find the file anywhere on my computer and I definitely didn’t delete it. I’ve worked for weeks on the project, and now all of sudden it says it’s gone and I can’t find it anywhere on my system. It was only after I opened and worked with the multi cam clips. Please help if you have any information…. my project is due today, Wednesday! Ahhh!! It’s really a problem that final cut just randomly did this. Thanks.