You can fax your invoice to the number for "missing stay credit" in England, +44-20-7012-7318, and ask them to look into whether the points credited were accurately determined.

If you're in England anyway, you could call that center (Cork Marriott Rewards Guest Services, +44-20-7012-7312) and let them know you have a question about that and will be faxing the invoice. That way they'll be expecting it, but you still should include a note explaining that you realize the nights credit for the stay was posted, and are inquiring about the number of points credited, so they don't think the issue is OBE because the nights were credited.