The transfer of a mineral ownership, like a transfer of a real estate ownership, requires a deed. To effect the transfer, the mineral deed needs to be filed in the county records. This filing puts the world on notice of who owns the minerals. It is the buyer’s responsibility to ensure the deed is filed in order to protect his interest.
You stated these were inherited rights. I assumed the minerals had been separated from the land some time in the past. This separation creates dual chains of title for the landman to follow.
Just curious, where in Milam County is the interest located?