OP, if you consider this to be a “very upsetting intrusion”, you may wish to either re-set your expectations regarding stuff that can happen when you travel or take your dollars somewhere else. Their policy has been communicated to you. Accept it or move on. Entirely unclear if you’re more upset about the perceived injustice of them checking on the room or your encounter with the manager. As with most stories like this, I’d love to hear the other side.