Happened to me twice last week.

Reservation for the Hanbury Manor which I cancelled at 11:32 am. Cancellation cut off was 4pm same day. The other was for the Portsmouth Marriott - cancelled at 12pm, cutoff was 4pm.

I cancelled both reservations online. It turned out that the reservation had been cancelled in both cases, but had not made it through to the front desk system.

I only received email cancellation confirmation from the Hanbury Manor. The Portsmouth Marriott showed up in the list of cancelled reservations immediately, so I thought nothing of it, but then it disappeared after a day.

I found out about the Hanbury Manor when they sent me a bill and about the Portsmouth Marriott when 191 (???) points showed up on my account.

The Portsmouth Marriott refunded my card almost immediately, Hanbury took about ten days to refund my marriott credit card which has a trailing balance on it, meaning I'm forking out for 10-15 days interest. Whilst not a lot, its more the principal. The GM said they would not reverse out the points as way of an apology - but they were never posted in the first place!

In future I'll ring/email the hotel well beforehand

David