I guess the difference is, when I began my quest to reach the seller (e-mailing, calling), I was only under-cutting potential buyers. Nobody had committed to buying anything, nor were any of the bidders legally due the watch.

I closed the sale. I negotiated and I paid for the watch. Once I paid for it, it was legally mine.

I do understand your point and I too have had items I'd been bidding on closed without notice. But I think we should accept that that's what happens when there's worldwide competition for a relatively small number of worthwhile items.