From: Rabbi Moshe Sofer
To: Rabbi Avraham Yitzchak Weinberger
A servant finds a purse lost by a non-Jewish customer in a Jewish shopkeeper's wine tavern, raising whether the shopkeeper acquires it via kinyan chatzer or the servant keeps it as finder. The Chasam Sofer rules the servant acquires the purse, both because the store's heavy foot traffic renders it an unguarded courtyard ineffective for kinyan chatzer, and because a servant's found object belongs to the servant absent specific instruction.
Source: Shu"t Chasam Sofer OC §44