A few Ideas.
Might suggest pulling the trim panel at the top rear of the vehicle and put a similar mark under it and try these ideas. See which one works best and does not harm the liner.
Ballpoint Ink Stains
Lay the stained area on top of a clean dry white towel. Apply rubbing alcohol to the ink stain and blot with another clean white cloth, removing the stain as you blot. Rinse thoroughly.
Lay the stained area on top of a clean dry white towel. Apply nail polish remover to the ink stain and blot with another clean white cloth, removing the stain as you blot. Rinse thoroughly.
Apply your normal liquid laundry detergent onto the ink stain and allow the garment to sit for 3-5 minutes.
Wash in the warmest water that the fabric can tolerate.
Before drying, double check to make sure the stain was removed. If not, repeat the previous steps until it is.