Why does this guy pop up in my head? I only dated him once, long ago?

I think you guys definitely had potential. He probably ignored you when you texted him because he was angry that you sort of played him, and didn't get his hints. Even though you didn't do it intentionally, in a way you were doing him good. I think you should call him, not text, and tell him you miss the old times when you guys could just chat and be together. Maybe ask him out for coffee. If you like him enough you'll ask him out. If he says no or is in a relationship, who cares, you tried. If you're thinking about him that much he must mean a lot to you, and you shouldn't let this pass. Don't be stubborn and give up a chance on a great guy.