I must give you the same disclaimer as valkyrie...I'm not in the position to give advice since I don't know the laws of your state or the specifics of your situation, yadda yadda yadda.
That being said, I think your BEST option is to at least talk to a lawyer. It may end up to be no big deal, but the only way you'll know that is to talk with someone with experience in the type of situation you're dealing with. One other thing, just because the officer was nonchalant on the phone doesn't mean HE even knew what he was talking about.
Just based on my personal (NOT legal) experience, it doesn't sound like you're in a huge amount of trouble, but I may be wrong. The only advice I'd give is to talk to a criminal defense attorney and figure out what you might be faced with on Monday.
I'm not certain of the laws in your state, but in California you would possibly be cited for a minor in possession (MIP) as well as the fake ID. I have a friend who received one of these in college and although they're a hassle, not a HUGE deal. Just be happy you weren't driving when all of this happened like my friend was....that adds a wrench into the situation.
