Mo. Rev. Stat. § 447.010: Duty of persons finding lost money, goods.

If any person finds any money, goods, right in action, or other personal property, or valuable thing whatever, of the value of ten dollars or more, the owner of which is unknown, he shall, within ten days, make an affidavit before some judge of the circuit court of the county, other than a municipal judge, stating when and where he found the same, that the owner is unknown to him, and that he has not secreted, withheld or disposed of any part thereof.