Amazing how many people at Marriott know that redemption stays earn stay credit. Upon checkout you should have received a $0.00 receipt (folio). Check your email, it may be there. Alternatively, call the hotel and ask them to email your folio. Once you have that, you can file a missing stay request attaching the folio. That should take care of it. Hopefully. Once I was denied my PAG points and credit on a redemption stay and needed to direct them to the T&Cs. Then everything posted correctly. Good luck.