Duke nukem forever save magically disappeared?

today my friend came over and we were going play duke nukem forever but when i was going to show him some of the chapters they were all gone and my friend play the 1st chapter after it so my continue save is also gone now, so is there anyways i can unlock all of the chapters using a cheat or save data or something because i dont want to play from the beginning because im pretty far in to the game and i am playing on the pc version.