@Ev123,
Just because you ask for a guys number, doesn't put you under any obligation to text him. And just because you text him once, this doesn't mean you have to text him again.
You guys don't have a relationship yet. I don't know why you think this is a big deal. People get busy or distracted or lose interest. Who knows?
If I were in your position, I would send him one more message. I wouldn't send an angry message (since you don't have anything to be angry about), just a 'hey what's up, I would like to talk to you again' message. Then I would move on. He doesn't owe you anything at this point, and since you guys have only met once there is no reason for you to be hurt.