From the PL website:
Once hotel rooms are purchased through priceline.com, they cannot be cancelled or changed by priceline or the hotel that accepts your offer and no refunds will be given.
Our hotel partners allow you to save up to 40% or more off the lowest published rates with priceline because we've promised that our customers are guaranteed buyers. This is the agreement that keeps this great service available and the reason we ask you to carefully review all the details of your offer and make any necessary changes before you click "Buy My Hotel Rooms Now" on our website.
Although you may want to give PL a call and see what they say: 1-800-774-2354
aloha