I agree. You handled the interview in a mature, correct manner. If it comes up again, then handle it the same way. It was the wrong thing to do, but you are older now and have learned from your mistake. We all have something we have done that we aren't proud about or happy with ourselves.
Don't assume that is why you haven't heard from the schools. It may be, but there is no point in trying to guess about it at this point in time.
If you get rejections from the schools, then I would suggest you meet with them and sit down and find out why they rejected you. Most schools do this as the cycle slows down. That way you can find out what happened and ask them what you could do to better your chances for next time.
If you find out it was the reason you were rejected I would suggest the following...
Why don't you contact some local high schools and ask them if you can come in and talk with some of the classes to tell them about under-age drinking and what it has cost you. Then you could show the schools you have taken the situation and used it to help others.