The retro active enforcement of rules is ridiculous and should be stopped. Once the round is over and the cards have been signed that's it. The scores cannot be changed after the round. In the NBA, NFL, NHL etc. when there is a blown call, the league simply issues a statement admitting yes the mistake was made. They don't go back and change the score and manipulate the outcome. If he knew that the penalty had been assessed during the round perhaps he would have taken a completely different strategy and his score would have reflected that as well.
If he was caught or turned himself in while the round was going on then that's one thing, but for him to wake up the next morning and see that he was assessed a two stroke penalty is dumb.
References to other sports don't work.