Yes, you can most definitely fix this. Honestly I can't remember why you can't move the winner in the Adjust Rankings dialog, but I'm sure there's a reason.
There's no reason you shouldn't be able to undo ANY bust-out. So, with the tournament loaded up, press the S key (or Undo Bust-out button on the Controls tab). You should be able to undo the bust-out of the player ranking 2nd (because the player ranking 1st didn't bust-out).
If the "Undo Bust-out" button on the Controls tab is disabled then no one is currently busted out, which would imply you don't have the completed tournament loaded.