Go to the restaurant and find out who the managers, bartenders, servers, hosts were that night, he could be a regular. If he was drinking then employees especially bartenders would notice it, atleast thats your job at a restaurant, and since most people dont use cash they would have the receipt with his name on it from that night and firefighters get discounts so those are usually kept in different files. I doubt the police will help you, they usually don't fuck over city workers if no one was hurt. You might be able to get some type of insurance claim against the restaurant too for over serving. I was a restaurant manager and have dealt with this issue a few times and it was really easy to find the people.