I had the same problem. Backed out to the main menu, and restarted the level, and it appeared. May have also restarted the game too, but not sure. It just magically appeared randomly for me.
Couldn't you jump on top of the moving ball spitting thing and crouch jump to grab the ledge then get that star in reverse? Haven't done it but it looks doable. I know I've been able to ride that thing before.