That actually wouldn't be a bad line if you ask me. I usually get around it by carrying two quarters with me. A regular one and a sate quarter, if they notice it's a state quarter they will almost never note which sate it's from. Just put them in opposite pockets and keep track of which pocket they're in, then when you see which kind they pull out for the trick, grab that one and continue. Or just offer up your own quarter, it's such a normal object that a spectator wont question it.