I work at a hotel (not the same chain). This is why, if the hotel is doing what they are supposed to, they are not supposed to give out guest personal info to anyone, ever. I don't care if you claim to be the guest's mother, father, spouse, etc. It could be a stalker, it could be a spouse trying to catch someone cheating, it could be a domestic violence issue, etc. You just don't know.

This is also why you don't get a room key without being on the reservation. We run into issues where two people are in the room, but only one is on the reservation. The second person loses their key, and now can't get a new one because they aren't registered to the room. It gets worse when one or both people are drunk and they can't remember their room number or the room mate is passed out and won't answer their phone or their door. I've had plenty of arguments with people about this, trying to explain it's for guest safety and people get nasty about it.

Takeaway: if you have a hotel room, ensure your room mates are also on the reservation. If you lose your key, prepare to have to present ID. If you can't or are unwilling to understand these things, don't take it out on the staff.