You got me there, I am thinking either someone messed with it trying to "fix it" for her or maybe pot holes? If the piston was frozen someone might have tried to help and somehow hit the clips holding the pad then it jarred loose. Problem is you are playing a guessing game unless she knows or says something like "yea, one of my friends thought they could fix it". My daughter had a friend like that once so finally I had to tell her the next time he tried to "fix" her vehicle I was going to go to his house and make him pay for and fix the damages he was causing. That stopped it right there.