You could sue either, though it may be easier to sue your insurer if you can't even identify the driver:1) Your insurer: you would sue them for breach of contract, on the grounds they are violating their contractual (policy) obligations by not paying for the front end damage; you would need to prove the damage was no pre-existing.2) The other driver: you would sue him for his negligence (carelessness) in causing you property damage.