It's funny anybody would be concerned about a front desk seeing your MR points and I believe someone above suggested maybe even "stealing" them. The front desk person could much more easily sell your credit card number. Or, if they were at all devious give your home address to their friend, since you are out of town and thus very easily for a criminal to break into your house. If I was to worry about something it seems those are more likely than a front desk clerk stealing your Marriott points.