And so I went off, and the helpful fellow at the post office said that it wasn't there, because it was out for delivery, and the delivery people worked at the other office, but that I could pick it up at his office tomorrow.
So, I came back home, and when I got here, there was a postal van out in front of the apartment, and a fellow walking back to it with an express-mail envelope. So I stopped behind him, jumped out, and asked if that envelope was for my apartment number. It was indeed, and he was quite pleased to have someone there to pick it up after all, and I signed for it, and that was that. And then I went and parked the car properly.
And now I have a passport, and can go to Canada next week, as planned. Yay.