Having a Loyalty Scheme that the guest does not know about is somewhat counter-productive. However to test the system many hotels are electing to set up a scheme and make it 'Hidden' (ie do NOT tick the box 'Open' in the Inventory/Loyalty Scheme section of the Booking Engine.
The consequence of doing this is that any rewards triggered by the guest will be stamped onto the Booking Confirmation that goes to the hotel, BUT NOT TO THE CUSTOMER. So if you have defined a reward you can decide if you actually wish to give it to the guest.