429.620.  Broker failing to file suit or answer in pending suit within thirty days after service on owner, lien is extinguished, service of demand, procedure. — If a broker claiming a lien pursuant to sections 429.600 to 429.627 fails to file a suit to enforce the lien or fails to file an answer in a pending suit to enforce a lien within thirty days after a properly served written demand of the owner, lienee or other authorized agent, the lien shall be extinguished.  Service of such demand shall be by registered or certified mail, return receipt requested or by personal service.  The provisions of this section shall not extend any other deadline provided by law for the filing of any pleadings or for the foreclosure of any lien governed by sections 429.600 to 429.627.