It sounds from his message that he really did intend to talk to you. If I was really suspicious I might wonder if he saw that it was you calling back and refused to answer the phone, but only jerks do this, and from what you've told me offline, he doesn't sound like a big jerk. I could be wrong.

It must be said that people DO flake. Sometimes I don't call someone even if I really mean to. And there's also the hottie factor. Is this boy extremely cute? If so he probably has a bunch of other girls hanging around, so his calendar is full anyway. Don't worry, they're all bimbos -- whereas I'm sure you appreciated him for the deep and beautiful person he is on the inside. Or perhaps that's how he felt about you, in a manner of speaking.

Regardless, if you really want this boy, I think you get one more chance. Call and leave the following message: "Hi, this is Sara. Give me a call if you want to get together some time." This will remind him of your existence, yet give him an easy out should he be dumb enough to want one.