Check your Autosave Vault
Do you also have previously saved versions of the project?
I use a combination of both the Autosave vault *and* resaving my current project under a different name every day, like “My Project_20080605” for today’s date because I don’t trust FCP not to cause corruption, as it used to do back in the version 4/5 days
I have on occasion lost work but usu. not more than until the last Autosave. I also keep the Autosave interval at 15 minutes.
However the caveat with Autosave is that the interval is reset every time you hit Command-S, which means if you habitually save your work after every change, you can go for hours with no Autosaves being generated.
My rule of thumb with FCP and saving/backup is to err *WAY* on the side of caution
Good luck
Lu Nelson
Berlin, Germany