Mo. Rev. Stat. § 376.785
What does not constitute waiver of defenses.
376.785. What does not constitute waiver of defenses. — The acknowledgment by an insurer of the receipt of notice given under any policy covered by sections 376.770 to 376.800 , or the furnishing of forms for filing proofs of loss, or the acceptance of such proofs, or the investigation of any claim thereunder shall not operate as a waiver of any of the rights of the insurer in defense of any claim arising under such policy.
(L. 1959 H.B. 252 § 7)