Bit late now but if you are about to do major surgery on a piece it may be worth doing a Save As first. That or leave the instruments/tracks there and Mute them.
Only other thing I can think of is to (assuming Win 7) right-click on the file and see if there is anything in Previous versions.
Sorry for your loss. In my experience losses like this are invariably for the better as the machine is simply editing what has no future - the universe is taking it back so you can have another (and hopefully better) go.