Usually once the charge hits your credit card/the folio gets sent to you it should go to Marriott. If the former's happened, go ahead & send in the proper documentation to get credited. It's a holiday weekend so you might want to wait until the beginning of the week.

Often I call MR vs. using the online form & then they have me fax the folio w/ a note stating the problem. Yeah, it's a bit clunky compared to online, but usually the agent tells me to address it to him/her, which helps w/ getting it posted pretty quickly.

Cheers.