Just *prior* to the big break-up, there were several larger 'somethings' that came off the shuttle and dropped back (slowed down) markedly from the shutle ... this is EASILY viewable on the video taken by WFAA CH 8 in Dallas.
One of their crews was preparing to tape a segment for another show out at Fair Park and shot some video of the SS coming over the Dallas area ...
You can see one easily identifiable piece of debris near the beginning that falls "above" the contrail. It is a large piece of silvery reflective sheet metal that is spinning...the rotation is evident. It seems this is a piece of the outer skin of the craft, possibly a plate from the left wing.
I have been wondering if the two fairly substantial pieces of debris with their own contrails, following somewhat behind the main body of the shuttle -- as is clearly visible in the early portions of several of the videos -- might possibly be the two wings? Their location behind and on either side of the shuttle would seem to be just where you would would expect detached wings to be.