I have a short time on my auto save as well. Have a problem one time you learn your lesson. I also got into the habit of hitting f9 (calculate) then f10 (save) after every big input. Like when I'm done with all w2 input, then done with all 1099-R input etc.  - I must save a thousand times a file. paranoid? maybe but better safe than sorry. I never leave a file open if I'm going to be away for more than a couple of minutes (bathroom or coffee run). 

you checked the delete file (waste basket)? Any file just under the default folder for where the returns normally save? Maybe a file with no name - or saved with some weird name?

Think you might be back to square one.