there is a chance that you can find the temporary files that the Arduino used
Excellent Hint !
I noticed under windows, that for every new arduino ( 1.0 ) start there's a new temp directory, so chances are that you even find some old versions, to make life harder for you.
In windows explorer, enter %TEMP% as the directory, to give you a starting point where to search for. It should be something relative to your user account.
Then do a search for files named as your sketch ( without the .ino suffix ) I guess you find some .cpp files