Hold on on physical retaliation or at least don't post in forums that you plan to do it, otherwise you might just get caught and then you're the one having problems with justice, even if you just plan on robbing him as he did to you.
(
Even if you
don't plan to do it, it isn't wise to post ideas of physical retaliation in the forums. On the off chance he gets robbed or vandalized by someone else through some random act of violence, you wouldn't want some investigation to find your joking posts and take them seriously, making you the primary suspect.