That is correct FlyWithoutWings. It is a rate available to Marriott employees for their friends and family and does require an authorization form to be eligible. If the form is not provided upon check in, the front desk will change the rate accordingly.
In answer to your original question, the Friends & Family rate did recently become applicable for credit. I believe the change was made at the end of last year. Therefore, if your Marriott Rewards number was on the reservation, the stay should go through.
Normal posting time is 10 business days from the check out date. If you do not see the stay post by that time, I would recommend calling Guest Services to have it researched for you.