Did you receive the contact details of the girl's dad? If not you could always go back to the house and ask him since he hasn't called you yet. Also, in case the dad is actually covering it all up for the girl's boyfriend, you could get your friend to keep an eye out and let you know if the boyfriend ever comes around again, then go over and ask him yourself.
If it's an accident and the boyfriend just panicked it's fair enough to just talk it over and get him to pay for any damage. However, if he starts to get cocky about the situation, waterboarding may be a good method to make him see sense.
Furthermore, pans of boiling water and fully heated clothes irons are good way of making people accept your demands. Just make sure that if you decide to use the boiling water / heated iron method you tape the guy's mouth closed first. Also make sure that he is tied down to a chair and that his hands and legs are restrained. Confiscate any devices such as mobile phones.