In high school, I was meeting a friend one afternoon. We usually walked to the bus together and had lockers on different floors, so we would meet in a particular spot before heading over. From where we were there was a long hallway leading to the main entrance, and we'd exit there. Passing through the hallway we see an acquaintance walking towards us, we exchange quick greetings (pretty much just "Hi Greg" "Hi Guys") but don't stop— we're in a hurry to catch the bus and he's heading the other way back into the school. It's a bit crowded, so it takes us about a minute to get out, but not too long. We come to the sidewalk and who comes walking down it from the opposite direction? Greg. My friend and I exchanged glances but say hi again and keep walking.

It's entirely possible that he could have just used another door and walked around to where we were, but in order to have done so he literally would have had to run around a distance that was twice as long, then doubled back to run into us again from the direction he was coming, because the only door from the direction he was coming was a fire exit that we were prohibited from using as an exit.