(a) Unless waived by the parties in writing, a party to a case or proceeding heard by a commissioner, within 15 days after the mailing of notice of the filing of the judgment of the court, may file a motion for rehearing by a judge of the court. The juvenile officer shall have no right to file a motion for rehearing of any judgment of the circuit court in proceedings under subdivisions (2) or (3) of subsection 1 of section 211.031, RSMo. (b) The judge shall rule on the motion for rehearing promptly. If the motion for rehearing is not ruled on within 45 days after the motion is filed, it is overruled for all purposes.