Disappearing files

I used the quick pad for 3 days at a convention. I put files in F1 F2 F3 F4 F6 F7 F9 and F10. There were some other files still in F5 and F8 from another day. I got a message saying there was a corrupt file and I needed to transfer files to my PC. I shut down the unit and when I came home, I turned it on, prepared to upload the files to my PC and found F1 F2 F3 F4 F6 F7 F9 were all empty. For some reason F5 and F8 that had older files, that I didn’t need, were still there. Also the last 2 files I put onto the Quickpad in F10 were still there. I called Quickpad and they tell me to send the unit to them and they will try to find the files. I fear I will never see them again. Please tell me if there is anyway to retrieve all my hard work.