Almost every driver has tapped an unoccupied vehicle; most of the time there is no damage. However, modern cars are designed to protect the occupants, not their paint job. As a result, even minor taps can cause a dent.
The law in Georgia is governed by O.C.G.A. 40-6-271: (Duty upon striking unattended vehicle)
The driver of any vehicle which collides with any vehicle which is unattended shall immediately stop and shall then and there either locate and notify the operator or owner of such vehicle of the name and address of the driver and owner of the vehicle striking the unattended vehicle or shall leave in a conspicuous place on the vehicle struck a written notice giving the name and address of the driver and the owner of the vehicle doing the striking.
The law, however, provides inadequate guidance when the owner of the vehicle cannot be found. If a person leaves a note, it may not be found. Also, the owner of the damaged vehicle may dishonestly claim there was no note left. In both situations, I have had clients arrested who, in fact, took steps to notify the owner.
My advice is to contact the police if the owner of the vehicle cannot be found. Most people choose not the contact the police because they want to avoid being ticketed for the accident. That is entirely understandable. However, a ticket for a minor traffic offense is far more desirable than a hit-and-run arrest for striking an unattended vehicle and allegedly leaving the scene of the accident.