Not sure, but around that time we were in the MK, and could actually see fireworks going off in the distance. We were in Frontierland, near Splash Mtn, facing toward the parking lot (Splash was on our right). SoG is not quite in that direction, but Disney property is so large, I'm thinking it HAD to be on property somewhere. I guess they have to test these shows or changes to them somewhere, right? Maybe that was it. I was puzzled myself.