if it was an honest mistake I believe he was embarressed (after all, he's a man for crying out loud! and you had the nerve to point it out, ) okay that was rude and I apologize to those men who do not have that attitude, he's the owner's son, how dare you point out a mistake!
OR, he did it on purpose and was embarressed to have gotten caught, again, how dare you!
If you have some other place you can shop I say "give 'em hell" if you don't then just make sure you keep a keen eye on your cuts and your bill, if he waits on you again, be sure he notices that you are really watching everything closely.