I wouldn't store underwear (or anything personal for that matter) in any bathroom which guests were going to use. Not after discovering I had friends who admitted to rifling in bathroom cupbards when they paid a visit! It wouldn't even enter my head to do that and I was horrified. Years later I was suspicious that a family friend was rifling through our house when we were out and so I set a little trap to see. I did the thing with the hair on my bedroom door AND on my underwear drawer and sure enough, when I came home and checked, both were disturbed. I challenged him outright and he admitted it but wait for the excuse - he said he was looking for a kitchen knife! The world is full of weirdos.