No refund
I had this as well, and was a bit annoyed
Called Diamond desk, they could do nothing. Called hotel, they could not do anything, it is just one of those things
Tried to claim on the website form, for Price Guarantee, as it was actually on Expedia cheaper as well, but they only give it do you if less than 24 hours.
It is a bit annoying, but seems little can be done, the hotel may be kinder to you!
Good luck ^