Driveway Damage

I hosted a get together at my home. Parking is always a problem since I live on a hill. One of my friends (not sure who), parked along the hill like many other visitors have done. Unfortunately, they drove over my neighbor's driveway and damaged the driveway, and also a drainage pipe.

My neighbor emailed the neighborhood. about it. No denying I had the party.

My question is, how do I approach my friend (I don't even know who) about repair costs? Is this something I just need to suck up? I feel very awkward about it.