Wow...thought it was just me. There's something about SEA...

I've also been told in SEA at the gate to return to security to pass through it again, as there was "no record of me passing through security" in the first place (for SEA-YVR on AC). Told them to pound sand as the flight was departing in 15 minutes, and returning to security from that gate necessitates a ride on the train.

If I "didn't pass through security", isn't that a major problem? What, did I come in through the roof?

I blame it on the cranky UA agent at check-in, who repeatedly berated me for making changes to my itinerary "only 12 hours before departure". The flight had been booked for 7 days, and I hadn't changed a thing.