I wonder what that was all about.

Sure looked it to me, but it could have been more. Maybe they were deliberately provoking the US into attacking it. If Saddam Hussein wants to hurt the US, he's going to have to hit US forces in the Middle East, and/or the US homeland preferably before the deadline comes. But he at this point would need a political pretext to start so early. Having the US fire on an unarmed ship would work, even if the unarmed ship in question was deliberately causing trouble.

I think a nice response would have been "heave to and prepare to be boarded, or we shall fire into you!"

*sigh*. I've read one too many naval fiction novels ...

I would hope the intelligence community would take note and follow up with some investigation (list of crew being first on the agenda.) Rather than all seeing it as just an odd event and giving it no further thought.