Mo. Rev. Stat. § 141.690

Should the provisions of sections 141.210 to 141.810, or any section or part thereof, be held at any time to be in conflict or inconsistent with the provisions of any law now or subsequently enacted, or in conflict or inconsistent with the constitution of this state, the same shall not invalidate or in any way affect any proceedings for foreclosure in rem under the provisions of said sections, which have been instituted or which shall have been instituted prior to the time of such ruling or decision, but such actions or proceedings may be prosecuted and completed in full the same as though all of said sections and parts were as valid as at the time of the institution of such proceedings.