The WMD we haven't found is still a threat. Tuesday, May 18, 2004 12:01 a.m. Yesterday's report that a roadside bomb containing sarin nerve agent exploded recently near a U.S. convoy in Baghdad isn't impressing most of the press corps. They're dismissing it as no big deal--though we'd guess it was a rather large event for the two U.S. explosives experts lucky enough to escape with only minor exposure.