Irony?

So while I was waiting to board my first flight for my HK trip I was standing next to a mother, daughter and the daughters son. So the mother was concerned because a guy they were sitting with had left his bags and didn't return. So she is conveying her concern to her daughter who replies with "I don't care, it doesn't effect me and my life". I understand that she doesn't want to cause an airport evacuation and I'm sure it was probably nothing, but the irony of the whole situation was that her son is standing there wearing a Ground Zero 9/11 baseball hat.