Absent a contract with your employer explicitly indicating the employer has a right to works you create or the specific work you created, ownership of a work can only pass to the employer if it is a work made for hire. See http://www.copyright.gov/circs/circ09.pdf. From the facts you provided, it does not appear this matter is a work for hire and you should retain ownership, although additional facts could change that opinion.
Good luck,
Todd
Answered on Sep 08th, 2014 at 6:41 AM