Actually, I have a response that may answer one of Ragnarok's questions.
Does anybody know (and I suspect Mark will if anyone will) what directions were given to the FBI agents searching through the rubble at the NY landfill sites? Were they specifically directed to look for personal effects and tissue for DNA analysis, or were they given a broad brief to look for any objects they thought might be of significance? And, on a rather more speculative note, since the rubble was searched by trained FBI agents, how likely is it that any such person would either fail to recognise evidence of explosives or associated equipment, or, having recognised anything of that type, to feel it was not worthy of note?
My feeling is that a trained FBI agent, carrying out a detailed search through debris at a designated crime scene, would as a matter of course notice and report any evidence of explosive devices, whether briefed to do so or not. It seems to me an extraordinary stretch to believe anything else. However, I'm open to correction by anyone who knows more on this subject than I do.
Dave