Half the points is the LEAST the property can do. You did your part -- you made a reservation and paid for the room. The hotel failed. If this was an IT issue, that's not the customer's fault. If you booked a room and have a confirmation, whether it is a regular paid room or a points redemption, you are entitled to a clean room. If the hotel can't provide you with that, they shouldn't have accepted your reservation. If they were oversold, standard oversale procedures apply -- they could have walked you to an equivalent property and provided you with compensation. Either way, you were right, they were wrong.