Mo. Rev. Stat. § 379.190

If any such fire insurance company shall fail, neglect or refuse to furnish blank forms of statements and proofs of loss to the insured, in case of loss or damage by fire, as provided in section 379.185, then such company shall be deemed to have waived the requiring of any such statements or proofs of loss at the hands of such insured person, persons or corporation, and upon suit brought upon such policy, such insurance company shall not be heard to complain of the failure of the insured to furnish any such statements or proofs of loss, any provision in any such policy of insurance to the contrary notwithstanding.