Mo. Rev. Stat. § 70.690: Member leaving system before eligible for retirement, disposition of his contributions.

1. In the event a member ceases to be a member other than by death before the date he becomes entitled to retire with an allowance payable by the system, he shall be paid, upon his written application filed with the board, his accumulated contributions standing to his credit in the members deposit fund.

2. In the event a member dies, and no allowance becomes or will become payable by the system on account of his death, his accumulated contributions standing to his credit in the members deposit fund at the time of his death shall be paid to such person or persons as he shall have nominated by written designation duly executed and filed with the board. If there be no such designated person or persons surviving such member, such accumulated contributions shall be paid to his surviving spouse, or to his estate if there is no surviving spouse.

3. In the event a member's membership in the system terminates, and no allowance becomes or will become payable on his account, any accumulated contributions standing to his credit in the members deposit fund unclaimed by such member or his legal representative within ten years after the date his membership terminated, shall be transferred to the income-expense fund. If thereafter proper application is made for such accumulated contributions, the board shall pay them from the income-expense fund, but without interest after the date payment was first due.