Thanks for the report! What actually happened is that the fumble was recovered by Arizona who then fumbled it immediately and it was recovered by St. Louis - which technically was a change of possession, so the game engine ruled it "right." What the problem really is is that the middle possession wasn't long enough to actually be a possession, because while the Arizona player had possession he certainly didn't have it long enough that it should have been ruled as such. I've seen this happen one other time, and it is in the "to fix" list.