521.570.  When execution returned unsatisfied, bonds to be assigned — judgment rendered on motion — damages. — Whenever it shall appear from the return of the officer upon an execution issued in an attachment suit, that none of the property attached has been found, or only a part thereof, and that said execution is not fully satisfied, the court shall direct the officer to assign to the plaintiff, his executor or administrator the bonds taken by him for the forthcoming of the property attached; and such court may, upon motion, render judgment in favor of the plaintiff, his executor or administrator, against the obligors in the bond, for the value of such property, or if the value of such property should be greater than the amount due upon execution, then for the amount due, together with twenty percent damages upon such value or amount.