Since you weren't at a school function there isn't much they can do, unless you had signed a school contract stating you would stay drug and alcohol free because of sports, I don't think there is anything they can do.
Well if your under age and you were drinking you can get in trouble. Don't know if it would be with the school or not, but people have gotten in trouble for posting certain things on Facebook. Everyone's obsessed with sharing their life, they don't even think that what they're doing is illegal, but they still post some pictures...and they get in trouble.
it is important to keep in mind that whatever is on the internet, will stay on the internet. there probably is no other option than to admit to it, which is probably what you dont want to hear right now. for this matter, it is important to do whats right -theComing Inc.