Originally Posted by
Obfuscate Freely
Is it possible that this guy wasn't the owner of the deck? He was new to the store, and obviously didn't feel that getting the cards back was a priority; perhaps he had borrowed the deck from a friend.
I ask only because several people have expressed the thought that keeping the cards is some sort of "punishment" for the childish temper tantrum you witnessed. You should consider the possibility that you are punishing someone else entirely.
Obviously, leaving your phone number with the shop should eventually lead to the rightful owner of the deck getting it back (if he wants it), but if the store owner is trustworthy, I would recommend simply leaving the deck there (doesn't he keep a lost-and-found?).