Mo. Rev. Stat. § 443.185
Any and all releases of mortgages and deeds of trust on lands in this state, securing the payment of any debt or obligation, which have been recorded in the office of the recorder of deeds in the county in which such land is located for ten years or more, and which purport to release any such mortgage or deed of trust and the debt or obligation secured thereby, and which purport to have been executed by the mortgagee or cestui que trust of such mortgage or deed of trust, or by his agent or attorney, or by any assignee, or his agent or attorney, or by the executor or administrator of any deceased mortgagee or cestui que trust, or of any deceased assignee, or by any person acting for a corporation which is either the mortgagee or the cestui que trust, or the assignee, of said mortgage or deed of trust, shall be deemed to be valid, and the lien of such mortgage or deed of trust shall be deemed to be cancelled and discharged, notwithstanding any defect in the execution, acknowledgment, certificate of acknowledgment, recording or certificate of recording of the same; except that this section shall not apply to any mortgage or deed of trust unless the debt or obligation secured thereby has been due and payable for at least ten years. Any person desiring to assert any right or claim which would be barred by this section may do so by bringing an appropriate action to establish such right or claim, at any time within two years after the passage of this section, but not thereafter.
§ 443.185, RSMo