I think the kind of explosives used in the bombing, known as TATP (triacetone triperoxide) cannot be detected by smell by any trained bomb sniffing dogs. It was the same stuff used in the 7/7 bombings in London and the stuff used by the shoe bomber. If anything was phantom, infortunately is is the explosure materials....oh and I fogot, the MSM.
Thanks -- I had no idea about the substance.