1) Never assume wrong doing when it could be a miscommunication somewhere along the line. Find out before assuming the worst.
2) No reason ever to not politely say, as soon as you're handed a wrong amount, " thanks, hey, I think it's supposed to be a hundred, right?" You'd find out right then and there what's up and who's to blame, if it's not a simple error. It's like locating a missing person-- every hour that passes without finding them, the odds drop dramatically of ever finding them, and after 48 hours, the chances approach zero. Same is true for collecting owed gig pay.
3) Whoever promised you the money-- likely BL-- is who owes you. Same low-key approach works here. My life experience is that 50% of the time when you're 100% sure someone screwed you, you're wrong.
Those are my "get paid" basics.
But to the story-- in the end-- did the drummer have the extra $? Did he know you were supposed to get it? Eff that guy forever if they did it on purpose. That's theft. Somehow I doubt he knew/understood, because it's not like you won't get caught immediately, pulling that crap. There's no positive end game to purposefully doing that.