I may have misunderstood the process - but afaik there is a seperate booking and redemption process. So you book the hotel. You buy nights at a certain category seperately. You then use the nights you've bought against a hotel of matching or lesser category. The hotel and chain have the right to vary categories of hotels. Which means there isn't a contract for a certain number of nights at the hotel chosen - only the category of hotel subject to availability - if you get my drift. I think it unlikely there's much you can do other than ask for a goodwill gesture but I guess you'll be lucky.