The black box thing is just stupid.
1. When a plane explodes in the air the heat can dissipate all over but in a building the heat is contained causing higher temperatures which makes loosing the black box more likely.
2. An entire freaking skyscraper fell on it. What are the chances of actually finding it? Ever sifted through a sky scrapper full of ruble?
Everything the conspiracy theorist come up with is dis-proven again and again and they just never stop. I used to have a bunch a links showing the faults in the arguments but it's pointless. You can use all the facts in the world and they just ignore it.
They don't want the truth, they want to prove that it is a conspiracy which is why they will always be wrong. They don't look at the facts, they fit tiny pieces to their theory to make it seem plausible.