It could be any number of things. Did you call him "dad"? Did you talk about Taylor Swift or "The Hills" all night? Did you ask him which side he fought for in the Civil War?
I'm kidding, of course. Why do you assume you did something wrong? It's not uncommon for one person to enjoy a date more than the other. It doesn't mean you did anything wrong.
Maybe he felt like there was just no chemistry between you. Maybe he thinks the age difference is too great. Or, maybe he thinks he did something wrong and is too embarrassed to call you. You never know.
Chances are you did nothing wrong, but, for whatever reason, he didn't think you were a good match. It happens. Put aside questions of fault and blame, and just chalk it up to "it didn't work out."
LOL.. love the tag "maybe he got hit by a bus"
"Did you call him 'dad'?" HA HA HA! :-D
Cary gave you a great answer. My only question is why not call him? If you want to see this guy again, why are you waiting for him to call you? If you contact him, and he makes an excuse about being too busy to get together with you or he says outright that he doesn't think the two of you should date again, then you will at least have an answer. You will know how he feels and you won't be left wondering. If you contact him and he does want to see you again, then maybe things will develop further between you and maybe they won't. These things take time. At least you will have given it a shot. I think knowing how he feels about you one way or the other is worth the time for you to call him. Much better than just sitting at home wondering and waiting to hear from him. Life is too short for that.