Schilling, whose Providence-based 38 Studios filed for bankruptcy in June, listed the sock as collateral to a bank in a September filing with the Massachusetts Secretary of State.
Schilling also listed a baseball hat said to have been worn by New York Yankees great Lou Gehrig and his collection of World War II memorabilia.
The Boston Globe first reported the filing Thursday.
38 Studios was lured to Rhode Island from Massachusetts with a $75 million loan guarantee. The state is now likely responsible for some $100 million related to the deal, including interest.