Tightslot, yes, a happy ending. It all worked the way it's supposed to.
Well, yes, but if I'm being picky....
1) It does seem to me that there is some confusion among various individuals and organisations - my cruise line for one did the right thing and submitted an electronic list to the US but their staff were ignorant.
2) As it happened when I arrived in Vancouver BC I did actually leave the US. But it was quite feasible that I might have been flying back from Seattle - there is plenty of public transport across the border - which would have required me to re-enter the USA. In the past I would have hung onto my I-94W derature record (I was still inside 90 days), shown it at the boder and surrendered it on departure from Seattle. I THINK (but I'm not sure and I can't find the documentation right now) my cruise line did make some provision for that possibility - they asked if we were leaving from Seattle but I don't know what would have happened if I'd said I was doing that.
Like I said, I'm being picky (it used to be part of my job). If was simply going a to b and back again I would have no problem with the way the whole thing works but I do have some questions about some of the bits around the edges because this is by no means the first time that I have not followed the a-b-a formula when entering and leaving the USA.