Sooo.. the top 25/30 floors pulverised the bottom 70 odd floors into dust. And then magically evaporated themselves.

Yep, sounds legit George.

"It all fell down, it vaporized, it just evaporated"

Yea... it doesn't work like that.

Study on nano-thermite in debris:

http://benthamopen.com/contents/pdf/TOCPJ/TOCPJ-2-7.pdf

That would explain the pulverization.