Remains have been found from all the astronauts
According to Reuters. Obviously, it does not mean all the remains have been found, but this is pretty good results considering.
Equally obviously, it seems that being precipitated into the environment at 200,000 feet and Mach 18 does not burn someone up as thoroughly as I would have guessed it would. Either that, or like the Challenger, the cabin portion survived reentry for a lot longer than I anyone would have thought, with impact being the main disperser of remains.
If I knew if the remains had all been found in the same basic location or not, it would be easier to deduce what happened.