This exact thing actually happened with two of my friends when I was a teen... one threw a drink at the other as a joke and it knocked his contact lens up under his eyelid. Should he have called the police?
Yes it's a stupid prank but it's an accident, he didn't intend to hurt anyone, and probably had no idea she was wearing contact lesnes. All that's required in a situation like that is an explanation of why it's a bad idea / dangerous... you don't punish people for a mistake as if they intended it.