Mo. Rev. Stat. § 30.060

In case of death, resignation, removal from office, impeachment or vacancy from any cause, in the office of the state treasurer, the governor shall take charge of such office and superintend the business thereof until a successor is appointed, commissioned and qualified except in case of impeachment, when no appointment shall be made until a determination of the matter is had, when, in the event of an acquittal, the suspended officer shall be reinstated in office.