My son just bought new 27" iMac. I logged on in Guest mode when he was finished. Later he woke up the computer and started working. It did not ask him to log in or mention it was still in Guest mode. He spent hours making a movie in iMovie, uploading photos, etc. Just after he logged off, I thought to mention I had been using Guest mode and I just read that all work would be deleted when logging off. Sure enough, his whole afternoon's work was gone. He could not find it in either Guest mode or when properly logged on. Is there any way to retrieve this? There was no warning to him at any point that he was in Guest mode or that his work would be deleted.