Wis. Stat. § 346.68: Duty upon striking unattended vehicle.

The operator of any vehicle which collides with any vehicle which is unattended shall immediately stop and either locate and notify the operator or owner of such vehicle of the name and address of the operator and owner of the vehicle striking the unattended vehicle or leave in a conspicuous place in the vehicle struck, a written notice giving the name and address of the operator and of the owner of the vehicle doing the striking and a statement of the circumstances thereof. Any such stop shall be made without obstructing traffic more than is necessary.