Need some advice

So two weeks ago, mine along two other co – workers cars were parked out in front of our work. A guy came hauling ass down the street and smashed into our parked cars unfortunately I only had liability on that car as it was an older model. He was at fault though. Have pictures and video footage. We got police report along with his insurance stated on there. With “national insurance” which has a bad rep. I’ve spoke with a claim adjuster from his insurance and they are claiming that they can’t state if he is “insured with them or not at this moment” and when they called him, He is claiming the car was stolen and that it wasn’t him. Which is bullshit because we saw him day of accident and police got his information that was stated on report and would of told us otherwise the day of. When I called them out on it and stated how can you not find him and you have the report with his information and stated you have him on the claim as one of the cars involved. they just replied yes I see that, I’m not doubting that but we still need to investigate and I will have to talk to my boss to see about how to further proceed. At this point what should I do? Do I file a personal claim against him and sue him? Do I keep hounding the adjuster. Any advice would be helpful. Thank you!