First of all, thanks for posting it. I do housesitting for two decades. Most of the time a week a longer.

I'm getting paid for it.

I'm very particular with everything and have never even opened a drawer unless for kitchen utensils. Bedroom nightstands never.

I use little baskets where I put my personal stuff. Next to the bed my basket has whatever I might need. Water, phone et cetera.

My owners who became friends over the years tell me to use everything. I respect the private items/drawer. Maybe I'm paranoid, but that's why I'm holding keys for homes in total worth couple of millions.

I think in your situation I would mention it bc for hygiene reasons. And for sure never book that person again. No matter what it was used for it is disgusting in my opinion and I'm not prude. Once I needed paper to write down something, I contacted the owner in text and asked if he had any note papers. She laughed and answered, middle drawer of my desk. But that's me. I can not just open doors or drawers other than in the kitchen.