When my Mom was pregnant with me, she became very ill and they operated...a ground breaking operation for the 1960's. She had an infection and had to have about 10 ft of her intestines removed. Now, that she is 70, when she has to have a BM, she has almost no warning...It's NOW. The story told by the OP is one of my mother's worst nightmares and one reason why she limits going anywhere. Luckily for her, this only strikes in the morning, so she is able to plan her day around it. Which is why we now only fly redeye to Disney World. (Can't exactly get up and to go the bathroom when the plane is taxing down the runway. Also, she's careful about rides in the AM, but she absolutely hates taking the bus in the morning.
Having said that, unfortunately, seems a little typical for teenagers. They don't realize that they will be old one day...To them, it's just not going to happen. That's why they have parents to teach them. Blame the parents, not the teenagers.