In a professional sense, look at the value achieved here: 'Buddy' saved thirty minutes by not copying the code and commenting his changes, and you lost six hours to find out what happened and additional time to 'unfix your mistakes.' Assuming the whole process took you 8 hours and both you and Buddy make $20/hour, I figure it like this:

(0.5 * $20) - (8 * $20) = $10 - $80 = -$70.

As a project leader, I have never been willing to spend money to compromise the team (loss of morale, trust, etc). Of course, I am a bang-for-the-buck kind of guy.

Short Answer: Buddy screwed up by saving time and the project lead screwed up by ignoring it. I would be just as angry. Take precaution in the future to protect your work and move on. If it happens again, Simon Travaglia has created a creative reference to inspire appropriate response. If nothing else, it makes for good reading!