How do I know Jupiter is rotating? Because I have seen it rotating through my telescopes. I take it you don't have a telescope then otherwise you would be able to see the same thing I do. I can send you images of the red spot moving across the disk if you wish. Not a problem for me. Images that I took by the way with my own equipment with no funding (sadly!) from NASA.
You see a red spot on the surface of any object and come to the conclusion that because you see the red spot moving the object must be moving?
I find this conclusion to be highly dubious.
I have observed Jupiter through a telescope in my astronomy class while in college. I wasn't able to ascertain any rotation.
Further, I doubt you are in possession of a 30K USD instrument of any form and fashion.
You see a spot on the surface of the object rotate around the circular surface, then come back into view every ~10 hours or so, regularly, on a loop, as if it's rotating. Yea, dubious conclusion, sure.
You looked at jupiter for a few minutes with a telescope years ago while not looking for anything in particular, I'm sure you gathered tons of data.
You don't need a $30k piece of equipment to view these things, although if you use google, you may find a local astronomy club with members who do have this equipment. I'm sure they'd love to let you use it.