That is quite the dilemma indeed! If you are still at the property, I would call Marriott Customer Care and explain the situation that you are on an Explore Friends Rate and wanted to know if Marriott Elite benefits apply to this rate? Once they confirm “Yes” then you can describe what is going on with the hotel and ask them to call the front desk on your behalf (whilst at the front desk) so that this can be sorted out if you are using your Platinum benefit for breakfast.