Mo. Rev. Stat. § 43.404: Parent or guardian may report missing child, when, duty to notify patrol when child located.

Any parent, guardian, or legal custodian may submit a missing child report to the patrol on any child whose whereabouts are unknown, regardless of the circumstances, subsequent to the reporting of such to the appropriate law enforcement agency within the county in which the child became missing. Each of the reports so made by any parent, guardian, or legal custodian shall be included in the records of the patrol concerning the missing child in question. The parent, guardian, or legal custodian responsible for notifying the patrol or a law enforcement agency of a missing child shall immediately notify such agency or the patrol when the location of the child reported missing has been determined.