Just grab the one you suspect most by the hair and yell "I'm going to punch you right in the fucking face!!" Now, punch him right in the face. Again. Once again.
Say "Who's the little bitch now, huh?"
"Who's the little bitch-boy, Nancy?"
Now, punch him in the face again. Harder. Again.
He should be pretty well collapsed by now. Sit down next to him and whisper, "why'd you do it? why did you steal my CC number?"
If he's like, "Dude, WTF are you talking about?" you might have the wrong guy. Go the the next guy and repeat the process.