You are not the first, nor will be the last with this. I suppose that you have read the first post on the Hotel Mistake Rate, what to do, what not to do. It kinda sucks you where not notified, have you checked your spam email folder? The few times I've participated and have been canceled, I received a notification to the effect of the error, the rate is $XXX.XX, and I have until MM/DD/YY to accept it, otherwise it will be canceled and I will be refunded.

Have you check if you have received a credit for the charges, at this point I highly doubt the hotel will honor the rate, however, maybe they can offer a discounted rate.