Doesnt matter whether he put do not disturb. Staff cant simply go in any occupied rooms. There are SOPs to be followed

I kena once in Sydney. It was a well known 5 star hotel. Was walking around the room naked when suddenly a staff opened the door, looked at me stunned and then closed the door. Thank god it was a female staff.

Straight away  called the conceirge and complained . They gave me complimentary free flow champagne & free access to their club lounge for the duration of my stay and also 1 night free stay.