Hmm.
Well, I'd probably be slightly miffed myself, lol... If he asked you to go, he's being pretty flaky in now taking a date instead.
But as much as I'd probably be pretty annoyed, I'd pick my battles. If he's just a friend, getting pissed at him for going with someone else (despite it being totally logical to a girl) will strike MOST guys as being completely insane. I don't think their brains work in quite the same way... they don't often seem to understand the things that upset us, hehehehe.
But yeah... hashing it all out with him in a dramatic way might harm your friendship. I might casually mention in a playful half-joking way, "Btw, next time I get ditched for a date, I'm returning the favour. Get you Astros tickets, then take a date instead.

" (Or whatever tickets he might like)
As for whether you're jealous... that depends. Like you, I have a close guy friend, we hang out a lot, but we've never flirted or dated. That being said, I've had a little crush on him for years. I'd never do anything about it, he has a girlfriend, and I'm just not that kinda girl... but do you have a crush on this guy? If so, it might be jealousy rearing its ugly head. Or it might be a normal friend-jealousy type thing. I know I get a bit upset if my girl friends ever ditch me for other people in general...
Anyhow, hope it all works out okay.
