What is the ruling on someone who collides with a person's car without knowing them, and is unable to reach them due to not knowing their information, despite potentially causing damage to it?

If you are unable to reach the owner of the car you damaged and cannot assess the extent of the damage, then you must repent, accumulate good deeds, supplicate for the car owner, and give charity on his behalf as much as is feasible, while humbly beseeching Allah to make him pleased with you on the Day of Judgment. If this is not possible, then you must increase your good deeds and return to Allah Almighty with supplication, imploring Him to make him pleased with you on the Day of Judgment.