County Recorder’s offices usually records deeds and other legal instruments. They frequently have a “miscellaneous” record where a wide variety of documents might have been brought in to be recorded so that an official copy existed if the original was lost. Have you searched through these records in the local County Recorder’s office?
In one Illinois county, the miscellaneous record contained out-of-state death certificates, a divorce decree from a divorce granted in Florida, my great-uncle’s medical license, military discharge papers, and more.
Give them a look over.