Mo. Rev. Stat. § 300.590: Warning of arrest sent upon failure to appear.

If a violator of the restrictions on stopping, standing or parking under the traffic laws or ordinances does not appear in response to a uniform traffic ticket affixed to such motor vehicle within a period of five days, the traffic violations bureau shall send to the owner of the motor vehicle to which the traffic ticket was affixed a letter informing him of the violation and warning him that in the event such letter is disregarded for a period of five days a warrant of arrest will be issued.