From: Rabbi Moshe Sofer
To: Rabbi Sinai
Community members sold their whiskey to a non-Jew before Pesach with a conditional document, but the non-Jew fails to pay and returns the chametz. The Chasam Sofer permits the chametz based on multiple grounds: the condition was halachically invalid (rendering the sale unconditional).
Source: Shu"t Chasam Sofer OC §119