Not guaranteed at all? The ceiling of an F-16 is lower. It's really not guaranteed that that would've worked. These missiles have limited range, and gaining altitude is costliest. It's entirely possible that a Sidewinder would not have worked from an F-16, requiring the use of a longer range, more expensive missile, and even that might not have worked as a balloon is a strange target and they picked this specific weapon system and platform because they believed it to have a high chance of success.

Why wouldn't you use your weapon system that has the highest probability of working on the first shot? The entire world was watching.

Yes the entire world is watching. That's what I mean by signaling.

And most of it is amazed how much sensation is made of this (:

Brazen invasion, I'll wonder if they (US or China) will release honest details, but I cannot imagine much real purpose there and for now only assume incapability/incompetence.

I mean I'm not trying to say what effect it had, but high altitude balloons have been downed by multiple countries without F-22s firing sidewinders. I think the choice of F-22 was deliberate because of the visibility. To send a signal.