Missouri Revised Statutes Title XXVIII. Contracts and Contractual Relations § 431.170. Action against assignor by assignee, when

(1) If he use due diligence in the institution and prosecution of a suit against the obligor, maker or debtor, for the recovery of the money or property due, or damages in lieu thereof;

(2) If the obligor, maker or debtor is insolvent, or is not a resident of this state, so that a suit would be unavailing or could not be instituted.