Mo. Rev. Stat. § 400.9-618: Rights and duties of certain secondary obligors.

(a) A secondary obligor acquires the rights and becomes obligated to perform the duties of the secured party after the secondary obligor:

(1) Receives an assignment of a secured obligation from the secured party;

(2) Receives a transfer of collateral from the secured party and agrees to accept the rights and assume the duties of the secured party; or

(3) Is subrogated to the rights of a secured party with respect to collateral.

(b) An assignment, transfer, or subrogation described in subsection (a):

(1) Is not a disposition of collateral under section 400.9-610; and

(2) Relieves the secured party of further duties under this article.