You can sue your father for the car--that is essentially what the officer meant when he called this a "civil" matter: that you need to bring it to civil court. You can sue for either the car's value (procedurally easier) or for a court order for its physical return (procedurally harder). You would sue based on theft: even then something is not the crime of theft, there is a civil cause of action based on taking another's property and not returning it.