The owner/operator/manager of the dining establishment can attempt to discover the identities of the alleged miscreants.
Most often, if the matter is in the hands of law enforcement, law enforcement has a myriad of ways to determine WHO was involved.
If you were NOT involved in the criminal operation, but know who pulled it off, it would behoove you to scamper off to the nearest police, sheriff, marshal, or constable to shame, name, and out the conspirators. If you're going to do right, don't wait, do it before the sunsets TODAY. If you continue to wait, as my beloved grandfather often said, "Study long, study wrong, boy".