[Sabertooth]

If they had done this, we would have detected it.

Agreed, if it was aimed at Alaska, but see my #23. I'm no expert, so my stratospheric fragment scenario may be nothing. Smuggling the warhead fragment in is another possibility, and not especially reassuring.

Or, the story could well be a complete hoax.

[judicial meanz]

From what I found,I think this ties to the attempted launch of an orbital vehicle by NK in August of 1998. There was speculation that some pieces may have landed in Alaska.

No one ever said WARHEAD pieces.

Your theory proves correct, Saber!