After I inflated the tire to 44 psi last night, it read as 36 psi this morning
Just before I left Ellensburg, it measured at 34 psi
I stopped at the Indian John Hill rest area, 25 miles out of Ellensburg, to make sure the tire was holding air OK; it was still at 34 psi
I then drove to Costco Issaquah, where I was helped by yet another impossibly friendly Costco employee who proceeded to explain that the tire was 100% covered by their road hazard warranty, which I didn't even know existed
He then ordered a replacement tire at no cost - it should be here next week
Finally, he insisted that he replace the tire on the car with the full sized spare [I declined as I need to sleep; I'll have them do that Saturday morning instead]
I then drove home, and after parking the car in the garage, noticed that it's making a soft hissing noise. Guess the tire is slowly deflating :)
That's the end of the tire story for now. Guess I ran over something that caused it to get a tiny puncture Monday morning; Tuesday, when we drove to Yakima, it must have already been pretty flat as there was a burning smell when we parked - oh, and yeah, a trucker flashed his lights at us, which in retrospect was probably a friendly "hey, man, your tire is flat" warning.