I suggest you talk to a lawyer.
You might have the defence that you where on private property where you don’t need a licence.
If that doesn’t apply, then plead guilty and explain to the judge that you “thought” you where on private property, and had no intention of driving on the public road. You might get a reduced penalty.
You will of course need to explain how the car got to that parking lot. If you admit you drove it there before the cop arrived, or he Saw you drive in, then you are stuffed.