Sounds like the camera suffered some impact, likely dropped to some hard surface. Sounds like those damages should be readily apparent when someone handled it.

If the daughter (the person used the camera) returned it to you and her parents never touched it - thus not know she damaged the camera, then this could be a teaching moment. I would have a gentle conversation with the parent. IF the parents handled the camera to return to you, then all is lost. There's nothing you can do.