I booked the hotel on Jun 23rd, and stayed for 1 nite on 27th. I chose "pay at hotel". I arrived at the hotel around 8PM and tried to check in, but the reservation didn't notice the booking, and I sent the booking confirmation email twice. The FO just received the email the day after.
In order to get my rest, I was offered by the FO to take the walk-in rate, I agreed. The next morning I read the T&C for cancellation, it's said that no-show equal min 1 night payment.
I paid more than the deal I got from hotels.com, I expect the accounting to sort this out and considers I stayed at the hotel using hotels.com. So I don't need to pay twice.