The initial warning about "20 suitcase nukes" was never followed up because the details of the story were easily debunked. Primarily, this related to the inability of a nuclear device to be of any use in 2004 if it had been smuggled into the U.S. in the mid-1990s (the fissile material is inherently unstable and requires constant replenishment).
Wrong. That's a fatal mistake to make.
The sub critical components have a half life of 24,000 years.