Mo. Rev. Stat. § 443.160: Personal representative may satisfy and deliver deed or release.

The personal representative of the holder or owner of any indebtedness secured by any security instrument, shall, if such indebtedness had been paid to the decedent in such decedent's lifetime, upon request of the owner or owners of the property conveyed by such security instrument, deliver to such person a sufficient deed of release of such security instrument.