[Sabertooth]

Apparently this is debris from their 1998 satellite launch attempt.

That would make sense. A fragment was found, and dubbed a "warhead" by a heavy breather.

Another possibility, is that the fragment is from an errant test missile that was self-destructed, and the satellite story is the sanitized explanation.

[Poohbah]

The DPRK announced concurrent with the 1998 launch that they'd successfully orbited a satellite. Independent verification of a satellite was never made.

Either they had their lies ready to go, or they really were trying to launch a satellite.