I've had that happen several times when I've gone to Julia's place, as she tells the girls not to lock the door even when they're busy, so sure enough someone walks in and then they have to get dressed, and after telling him they're busy, then she gets undressed again...a real pain and so what I try and do is lock the door when they're not looking after I arrive. Doesn't always work as then the client rings the bell so off they go to tell him they're busy. I suggested they get one of those signs that says Back At...and it has a clock you set the time to...but that's too easy!