How do you find someone you only met once?

I drove my friend to a lecture that evening. A small group of men was standing there, waiting for the exam to begin. I noticed a guy sitting on a wall. He was separated from the group and quiet.I liked the way he looked, that smart face, smart eyes. The other men went to a different room and my friend, him and I went to out classroom with the professor. My friend and the guy were revising with the teacher and I joined them. I didn`t pay much attention to him then. I only looked at him a few times and he looked at me a few times. That was it.After the class, he needed a ride (it was late in the evening and he would have had to walk to the bus station). I gave him a ride. My friend was talking to him and I was quiet, I barely said anything. I realized I really liked him only after he left that evening. We found out his name from a friend who knows him, but I am not sure if I`ll meet him ever again. I cannot stop thinking about him.I don`t even know if he is single.what should I do now?

thanks Michael.
I already tried to find him on facebook, but he isn`t a memeber :(

Here's a suggestion: go to craigslist.org and choose your city (or wherever you met this guy). Then click on "missed connections." This is a forum where people just like yourself search for lost loved ones or simply cute encounters. There are also "missed connections" classifieds in your local newspaper. Good luck, I hope you find him.