Mo. Rev. Stat. § 475.325

If upon the final settlement of a minor's estate, made upon his arrival at eighteen years of age, the residence or whereabouts of the protectee is unknown to his conservator or the court before whom such settlement is made or if the protectee refuses to accept and receipt for the balance found owing to him before the time for appeal from the settlement has expired, any funds remaining in the conservator's hands shall be ordered paid into the state treasury in like manner and subject to the same provisions in favor of the protectee as now provided by sections 470.010 to 470.260 in cases of nonappearing and nonclaiming distributees and legatees.