If neither Marriott nor the Cosmopolitan will honor the published rules for a Marriott Platinum member who has a legitimate reservation at an Autograph Collection (Marriott) property, then this reflects very badly on both.

I would hope and expect that with proper escalation, higher-level representatives of either entity will do the right thing.

Not only that, but it needs to be a high priority to fix the data for the Cosmopolitan on Marriott.com. Because such an age restriction is unusual and unexpected -- and not even uniform within Nevada -- it needs to be absolutely clear within the reservation process and clearly spelled out on the reservation confirmation.

Marriott should never answer something that's clearly wrong is the hotel's fault. Marriott should go to bat for the guest.