Have you noticed that people are possessive of their department bathrooms? You see a stranger using your bathroom and the only reason is because they don't want to stink up their bathroom in their area. Of course, they try to act all sly and all, but we know what's going on!
People look for the most secluded restroom, and of course it's usually a guy since women will generally wait till they get home. If someone is in the restroom as you walk in, they flush, cough, ruffle the newspaper, etc...to mask any incriminating sounds and want you to leave really quick so they can continue their business!
Who knows what I'm talking about?