Missouri Revised Statutes Title XXXVI. Statutory Actions and Torts § 525.270. Claimants of debts assigned, or property sold, may be made parties, how--notice, how given--trial

1. If the garnishee disclose in his answer, and declare his belief, that the debt owing by him to the defendant, or the supposed property of the defendant in his hands, has been sold or assigned to a third person, and the plaintiff contests or disputes the existence, force or validity of such sale or assignment, the court shall make an order upon the supposed vendee or assignee, to appear at a designated time and sustain his claim to the property or debt.

2. A copy of such order shall be served upon him, as in the case of a summons, if he can be found; if not, it shall be published once a week, for three consecutive weeks, in some newspaper published in or nearest the county in which the action is pending, which shall be equivalent to service. If the party so notified fail to appear as required, the garnishee's averment of such sale or assignment shall be disregarded; but if he appear, and, in writing, filed in the cause and verified by affidavit, claim under such sale or assignment, a trial of his right shall be had, without unnecessary delay, upon an issue made thereon; and if the same be determined in his favor, the garnishee shall, as to the property or debt in question, be discharged.