From fig. 1 on the second page of pdf linked by spenrose below, it looks like vapor cloud was more doughnut/torus-shaped than spherical (due to rotation) and lasted few tens of years.
I'm imagining that, as the hot gases cool off, and condense onto floating debris, the molten/solid debris field will probably look pretty nebulous, and then settle into unstable bands. At that point, I figure the torus shape would be very apparent.
Once the hot gases were gone, I bet it probably took a while for the rest of the debris to get swept up into decaying orbits, and impact on either body (earth/moon).
If they could visualize it with a simulation, it'd probably be fun to watch, and tweak the parameters of the event.