[justfallinginlove]

The girl obviously didn't want you to know for some reason

I'm going to have to disagree with this. We don't know what the girl was thinking or how she was feeling. She may not have had a chance (or means) to tell him before her parents made arrangements.

Although I do agree that you should just wait, as hard as that sounds. If you really can't help yourself, then, like Kelly said, you could always try calling her parents. Make sure that you are ready to step up before you do this though.
Also try talking to a trusted parent, guardian, teacher, counselor, etc. about the situation.
Good luck!