This happened to me at the old HI ORD which became a Wyndham a few days before my stay. I did my stay and sent a copy of the folio with a covering letter to the PC centre and a few days received stay credit and points for the stay. In my case it was only one night, but give it a try. They might not give you 100% of the points you'd otherwise have received, but would likely offer a 10K or so in compensation. Not quite what you may have earned, but worth a try. Be polite and not demanding...