Mo. Rev. Stat. § 451.190: Record supplied by certificate of witnesses, how.

If the minister or officer who solemnized any marriage, the record of which has been lost or destroyed, be dead, refuse to give a certificate as required by section 451.170, or his whereabouts be unknown, it shall be lawful for two credible persons who witnessed such marriage to make affidavit to the fact, giving the names of the persons, the name of the minister or officer officiating, and the date of such marriage, which shall be filed and recorded in the recorder's office of such county, which affidavit, or certified copy thereof, shall be prima facie evidence of such marriage in any court in this state.