I believe the focus of the argument is that:
(1) The 'staff' told an unidentified/unknown caller that she was there, and what room she was in.
(2) The 'staff' booked him a room right next to hers.
(3) The 'staff' had been modifying the peepholes for their own devious purposes, which is where he learned how to do it.
There are many articles out there on him. He was obsessed. He ran background checks on her, etc.
As far as the hotel not knowing. It does not matter. You obviously do not travel often.
Here’s the skinny. A hotel is not allowed to give anyone your room number. If you come into a hotel and claim to be a family member of Snark, the absolute most they are allowed to do is call my room and tell me “Mr. So and So” is down stairs and wants to talk to me. I can give that person my room number. The hotel can not. This hotel did.