In reality going forward any fan at a live event has to have a game plan for this type of situation. If you get a football or fly ball at a baseball game, immediately leave the stadium. DO NOT stop and talk to anyone.
This dude got caught lackin. He may not even have known it was 600. But it's tough, you got security asking you for the ball, fans probably egging him on to give it up, etc. Every minute you stay is a minute that makes it more difficult to leave with the ball.
Once you leave the stadium you have time to sit, reflect and make a list of demands. Can't think with that kind of clarity in the heat of the moment. This is life-changing money we talking about - dude got played bad.