You can contest a parking ticket if you want to. Follow the instructions on the back of the ticket to request a hearing. If you choose to contest the hearing take pictures of the location along with pictures of the location of the sign. If your friend is able to attend the hearing bring her and have her testify about the conditions and the viewability of the sign. Because the ticket is for a non-moving violation it will not appear on your driving record. The fact you did not actually park the car there is irrelevant. Your car was cited not you.