At least in the USA security has every right to search you, and throw you out for any reason - at a private venue. They aren't bound by the same laws as cops searching your person, home or property. When you buy a ticket into a venue you have given up many of your basic rights to be allowed access to the club. If you tell them no, they boot you out. I've known plenty of bouncers and many of them to confiscate, and smoke/snort/eat/drink what they find later. And will admit it "off the record". Half of them are roided and uppered-out anyway.

taking a glass bowl to a hardcore show? thats pretty brave... i've never been at a metal or hardcore show where a glass bowl would survive! Bring a cheap one or some joints next time. and just remember, they can call the cops on you... or beat the shit out of you if you look at them funny. You've paid admission to give them that right.

I had a buddy who used to take pot into shows all the time. he'd put it rolled tight down his crotch or whatever, and hide a dildo or tampon on his person... like a pocket or his jacket pocket. the guards would find the weird stuff and be like, "you sick fuck" and 9 out of 10 times just push him through...