From: Rabbi Moshe Sofer
To: Unknown recipient
The Chasam Sofer provides a novel explanation for the Rambam's ruling that a buyer who acquires stolen property through ye'ush and shinui reshus must return the monetary value to the original owner. Drawing on the Magid Mishneh and the Ra'avad's concept that the acquisition came 'through prohibition,' he argues that shinui reshus derives its effectiveness solely by analogy to shinui ma'aseh; by the dayyo principle, this analogy extends only to acquiring the physical object, not to retaining the monetary value. He further distinguishes that the obligation to return money applies only where the robber-seller gave achrayus, while takanas hashuk protects the buyer where no guarantee was given.
Source: Shu"t Chasam Sofer CM §56