Wyo. Stat. § 34-5-105
Any and all mortgage releases and assignments of mortgages which have been heretofore recorded in the office of the county clerk of the county wherein the real estate therein is affected is situate, and have been of record five (5) years or more prior to January 1, 1935, purporting to cancel and discharge or assign any mortgage, and purporting to be executed by any mortgagee his agent or attorney, or by any assignee of said mortgage, or purporting to be executed by any person acting for a corporation which is either mortgagee or assignee of said mortgage, shall be deemed to be valid, and the lien of such mortgage, shall be deemed to be canceled in case of release, and the mortgage deemed duly assigned, in case of assignment, notwithstanding any defects in the execution of such release or assignment. Provided, however, that the holder of any mortgage or the assignee thereof, which said mortgage is defectively released, or assigned as hereinbefore specified, and which has remained unchallenged, by the proper action in court, or other legal and proper proceeding, on the records aforesaid for the period of five (5) years or more as aforesaid, shall have until the first day of January, 1936, in which to commence an action in a court of competent jurisdiction in this state, for the assertion and enforcement of his rights, or to set aside such release or assignment, and if not so commenced as herein mentioned, then such release or assignment shall be deemed valid against such persons and all rights as against the same shall be barred.
W.S. 34-5-105