My Burgundy Iceberg does that from time to time. It's interesting that my Brilliant Pink Iceberg never has.
My Hocus Pocus bushes have sported back and forth all over the place. The most typical is for it to revert to Black Beauty and stay there, but I've had BB sport back to HP. Once I had a bush with HP, BB, and the original parent Frisco all on the same bush. I'm keeping my fingers crossed that Alakazam and Simsalabim don't sport back, since they're extremely attractive, unique, and hard to find. (All of those are sports in the same family).
Last year, my Sunset Celebration produced one bloom that was 1/3 dark pink, which has never happened in the 20+ years I'd been growing various plants of it. Sports happen!
