When this happened to me, as posted above, I called the hotel directly. Their first response to me was that their records showed I checked-in and stayed. I asked them to specify what records they were talking about. I asked them if they had anything with my signature. After a search, they had absolutely nothing.

If I were you, I would call the property, ask to speak to bookkeeping, and discuss with them. Ask them what records they have to support their claim that you checked-in and stayed. Since you never checked-in, they will haved absolutely nothing. In my situation, I have no doubt that somebody on the hotel's staff helped a friend to a room, at my expense. Or it could be simple (or grand) incompetence. It ended-up with the hotel providing a credit for the charge, and profuse apologies. I'm guessing you will get the same.

Finally, if Marriott business services left it as "the hotel claims that I indeed was there on that day and checked-in", without inquiring further (like to ask what records the hotel had to support its claim), shame on them.