In retrospect, Alaska/Horizon's mistake was telling us that the plane was going to be held in Seattle and then not holding it even when we were apparently on approach (the first time). Of course, since there were only 14 of us they probably had some numbers already run that said "oh well, send the plane."
Hopefully tomorrow night's flight will not have a problem, given that it's the LAST flight out. I don't want to stay another night.
And thus endeth the worst travel delay I have ever experienced (both in absolute delay and in delay as a percentage of original travel time). Knock on formica.