The results are in at http://www.senate.gov/legislative/LIS/roll_call_lists/roll_call_vote_cfm.cfm?congress=109&session=1&vote=00358.
Seems the lone non-voting senator wasn't Cantwell as I had previously thought - somehow, she cast an absentee vote of Nay from Iraq (perhaps I need to learn a bit more about how the Senate votes). The senator who didn't vote was Chris Dodd (D-CT). Why not? Nothing I can find - no statement on his website about it, just a Not Voting on the record. I used to live in Connecticut, Dodd was there when I was in the early 80's, although I think he was in the House at the time.
I'm still not happy she wasn't in D.C. when the vote was cast, but am a bit chastened by the fact that she did vote Nay. I still don't think it was her job to oversee foreign elections, though.