Mo. Rev. Stat. § 241.190

Whenever the county commissions of this state shall have sold swamp or overflowed lands to which they are unable to make a good and sufficient title, the said commissions are hereby authorized and empowered, with the consent of the purchaser, or, in the case of his or her death or absence from the state, then with the consent of his or her sureties or legal representative, to cancel said contract.