Wait, This Window Is Transparent?? Dept

This story (key sentence: "They couldn't see us or hear us and just carried on regardless as we all cheered") reminds me of a friend's experience some twenty years ago. My friend worked on the ground floor of an office building that had floor-to-ceiling windows covered with the reflective film that keeps out the August Austin sun. One of the grounds crew, newly immigrated and unaware of the whole concept of one-way mirrors, needed to relieve himself and found a nice secluded corner of the building...right behind my friend's desk...