Lost "Saved" file

PT11, recorded Demo Session, Saved, Mixed, Bounced to Disk, now gone. Where did it go? This has now happened twice and it shows no where on the computer. I had thought maybe I didn't have enough Disk Space left but I still have over 200Gb left on the HD so I don't think that is the problem. I had even backed it up in another file and it is also gone. Anyone else run into a problem like this and have a solution?