I had something similar happen at the Westin in Princeton about a year or so ago. They were in the process of refurbishing it (used to be a Marriot, I think) and were not open for business at the time I made the booking - about 2 months before I was due to stay. The rate was superb, something like $70 for an executive room, and not pre-paid so was still cancellable. However when I checked on SPG.com just be fore my trip, the booking was still there, but with a different booking reference, and a VERY different rate ($300+).
I still had the original confirmation email, so I forwarded that to *W and they (eventually) put it back the way it was. No excuse offered, or apology for that matter, but I was lucky I had evidence of the original booking.
I would have thought a quick email to customer service (hah!) with whatever back-up you have might get some response, but I dare say they won't back down now they have your money.
So your experience is not unique. Sorry I can't be of more help.
Sleepy