Called the hotel this evening "just in case", to be sure that they knew about the reservation. They couldn't find me in their database. They couldn't even process the confirmation number hotels.ca had given me.

Interestingly, hotels.ca doesn't seem to have any phone customer support people, so I have to go through their web-form interface. Glad I'm not having to do that while standing in the lobby of the hotel!

Hotels.ca still shows the room as booked, so I'm sure it's just a matter of not getting the reservation properly moved to the hotel database. Very happy about thinking to call though.