Call the front desk ask for the email information; general manager or dining manager. I believe their website has a link for communication. Both however will use your email address. Just make sure whatever email address you use is not in the Marriott system or use a close friends account. You will need specific information if they can't contact you.
Why file a cowardice anonymous report... if you were done wrong it's fine to speak with management directly... call the main number.
Thanks! Your answer is awaiting moderation.