There's a couple of things I would like to touch base on.
First, I'm sorry that this RN was unprofessional and rude enough to belittle you in front of others like that. She should have pulled you aside in private and had a respectable conversation with you there.
May I ask what kind of questions you were asking? I've caught myself several times asking questions that I could easily of answered myself if I just opened my eyes and looked what was right in front of me; leading me to start to annoy the nurse I was with. I agree with Gina, that a student should be able to ask any question they want. But they should know which questions to ask and which ones to do a little footwork on. I know, I'm guilty of it. (I'm saying all this without knowing what you said, so please don't infer that I'm inferring anything about you).
Given what I just said, I really think you should throw your "coupon" idea out the window. If you have a good question, by all means ask it!