Rossie: I've did it once, and later the organizer didn't want to give it back without any payments yadda yadda yadda. I stood my ground, and said I would walk out of here and report it to the police of them stealling my IC. Guess what? They gave me back.
thaaats right. if them organisers are a bunch of people thats what they should be told.
if its a venue, perhaps it'll be a little trickier. the IC was given voluntarily, under some sort of agreement between the two. perhaps, yes, its not legal to be holding on to someone else's IC but you practically handed it out to them because you want to play.
Going to the police is the right thing to do, and if you have no pressing need for it at the moment, please do. Because it'll take you 6 mths to a year to get it back, with pending investigations and all that. that is, IF it goes thru an investigation. if you call the police and they come, the matter will be resolved right there. The police will, however try to make a deal between the both parties involved, just to be fair. Something was broken, someone has to pay for it. But to slap charges against someplace for holding your IC is very tricky business.
I really have to check if its legal to do that, because it happens at all the pool places. Perhaps a valid arguement was that your age had to be verified. Gas Haus is, a club/pub after all.
Bottomline is, dont hand out your IC. If they lose it, what are you gonna do? They can say they never took it, and you had no proof. They'd just lose some reputation thru your small circles. And you have to pay for that IC. If you really have to hand out something, give an EZ-link, perhaps. Claim you already lost your IC.
And if they're asking you to pay for it, and all the negotiations fall thru and you are too lazy to call the police, just get a new IC. It will cost less than a $150 cymbal, and if you do manage to get back the 'lost' IC, you'd have two ICs. Which is illegal, too, but hey. Who's gonna find out? =D