What is wrong with me?

I was at a party Saturday, and a lot of people were there just to score girls you know (I'm a girl too). I was having a good time, and at some point a guy came over to me and we started talking, and he was incredibely nice, he wasn't trying to get me immediately, but he did ask my name to add me on facebook quite quick. We talked for a very long time, he bought me a drink, we really hit it off I think. He said repeatedly that we could meet again sometimes etc.He wasn't the most handsome, but average, but I liked him a lot. At some point my friends wanted to leave so I said I had to go, gave him a hug and he kissed me on the cheek, and I left. Now it's monday, and he didn't add me on facebook yet, and I don't know if he still will. I'm not sure what I did wrong. Did he forget? Doesn't he want to anymore? Or is he just waiting a few days before adding me?

He is a bit older than me, he's 20 and I'm 16, but he said I was very mature. Is it that we didn't kiss? Doesn't he know I want him to? I don't think I'm too ugly or anything, because he did come to me etc.

Basically, I just get tired of guys flirting with me and just wanting to score for one night and forget about me, and I don't know why, but I thought he was different. Maybe I should add him myself, cause I did look him up on facebook, but I'm not sure it's him. You probably don't know either why, but I'd like to hear it anyway. I know I'm overreacting, it's just driving me crazy.