If you discover that a bottle is empty, a simple stop by the front desk to let them know and it’s taken care of. My conditioner bottle was empty at POFQ in September and I just popped by the front desk on my way to the busses and when I got back that evening, all the bottles had been filled. (I was able to make it work as I had some spray that helps with humidity but also detangles, but if it’s a concern, check it as soon as you get into the room.)
I always bring my own soap, shampoo, and conditioner because I have sensitive skin. Hotel brands are not hypoallergenic normally. Better to be safe than sorry.
We were just at AKL. Individual bottles of shampoo, conditioner, body wash, mouthwash, body lotion; the kind that mouse keeping leaves when they clean the room, and I collect each day so that they leave more.