Save work deleted in Guest Account.

I'm an animation teacher with a brand new iMac. I set up a guest account for my students to play with and record work while having my personal account as Admin. For two days, the kids used iMovie to imput and save their projects in the guest account movie folder. At the end of this, I shut down the computer (previously it had been on stand by), coming back the next day to grade their assignments. Imagine my horror when I can't find ANY of the saved files.

I'm frantic. Should a guest account retain saved work? If so, how do I retrieve it.