Yeah its very sad. They said the biggest piece they have found so far is 4'. They didn't say of what.
I remember actually getting to see what the space shuttles were made of. The white & black areas you see on the outside are a very soft foam like material. You can put a dent/cut in it with your fingernail. Its made to withstand temps of ~7000+ degrees.
http://www.msnbc.com/news/857733.asp?0cv=CA01 - video of the shuttle