And yet all that paper survived. It's the weirdest thing to think about. Two buildings and all those people basically vaporized, but there's paper artifacts to find. Paper all over the place on 9/11, not burning, while everything else was in flames.
Watch the videos of the collapse -- notice all the billowing white clouds jetting out the sides of the buildings even as they're falling.
It looks to me that when each floor pancaked, the air that used to be between the floors was forced out at high velocity (it *had* to, there was no where else for it to go, just as a large book dropped flat onto the floor will blow away any light object within several feet of it).
It not only forcibly blew out the dust from the collapse itself, but it surely must have taken with it anything in the offices that would have been liftable by a high wind, including huge amounts of papers and other light objects.
So I would expect an awful lot of paper to have been blown out the windows of the towers as they collapsed, only to flutter down to the surrounding streets, clear of the crushing collapse itself and subsequent fire.
Paper is light - phones and bodies are not. As the WTC collapsed, with the floors pancaking onto each other, the air between the floors was forced out by the collapsing action, taking with it anything light enough to be caught by the wind