I rarely do pre-paid, but when I did it at Hilton my cc was charged before check-in (ie, charged at time of booking). That actually turned out to be a good thing because, during my flight, the cc company canceled the card when they couldn't reach me because they thought a legitimate purchase was fraud.

I agree w/ Kacee that one should always look at rate details before booking. Also agree that the deposit becomes the guarantee against the cancel if the OP cancels within the 21 day window. If he doesn't spend $800 during the award stay, then yes he'll get the refund on his cc.

Cheers.