From: Rabbi Moshe Sofer
To: Rabbi Sender Meizlish
The Chasam Sofer sides with the Beis Shmuel against the Chelkas Mechokek, ruling that when a wife invalidly sells her nichsei melog property, the proceeds must be returned to the buyers because the case is analogous to stolen goods, not to a spent loan. Unlike loan funds whose derivatives belong to the borrower, the money paid by buyers in an invalid sale retains its identity as the buyers' property, and the husband never acquired it.
Source: Shu"t Chasam Sofer EH II §163