I don't think he had any serious feelings for her at that point, (since I don't believe in love at first sight) but he was probably interested in this person who would approach him when he's so obviously an introvert (I know that most people wouldn't bother talking to me...maybe that's a good thing) and he probably also enjoyed himself while dancing.(once he could succeed anyways) That's what I think.

EDIT: Getting back to the original question...I think he probably would have realized after a rather long time, but instead he just got lucky.....