Arrrggghhhh!
I just used PL HK (the onlu PL that will accept my Canadian CC) to book a 3 day stay near LAX and paid a fee to switch my flight home to a red-eye to get around paying for a fourth night... I'm an idiot.
The popup window that contained the offer actually came up when I made my booking, but as I was on dial-up at the time, I shut it down before the graphic had a chance to load. Oh well, live and learn.