I won't sit on a stall in an airport unless I am in pain. And I wouldn't wait for a stall to open if my life depended on it. I need at least 10 minutes to clear the air before I will use a stall that someone else has been using.
There are hundreds of restrooms at the Minneapolis Airport. There is never a need to wait for a stall at an airport, especially one like Minneapolis. He knew that this was THE stall. The police knew too, that's why they set up shop at the stall next to it.
Correct, P-Marlowe, if he truly had an urgent call of (unperverted) nature, he could find another restroom in 10-20 seconds with vacant stalls.