Most likely your mother has inherited this mineral right and the person she inherited it from signed a lease.
The most likely reason for lost heirs is that someone moved out of the parish - and/or didn’t have a succession/probate open. Only in certain situations are the oil companies going to put a lot of effort into finding you because it’s your responsibility to fuel file the required paperwork’s in the parish to transfer ownership in the public records.
If the oil company cannot find you - after some specified length of time they are supposed to turn over to the state unclaimed property find. So you could check her name, her parents name, etc. it’s going to be in the name of the last that had title for to prove ownership.
To find it: Start with her parents and run them grantee. You are looking for any deeds into them - or any judgment of possession - which is what is filed here that is akin to a private elsewhere. If you find a deed you then need to look for the deed out and you are looking for any mineral reservations.
if you get lucky and the property is listed in the judgment of possession. However, it is not required to be listed in order for transfer of ownership to heirs.
If nothing comes up for her parents - the people most likely to have transferee ownership to get are parents, grandparents, uncles and aunts who died with no heirs. The best place to start is probably determine if any relative ever lived in caddo parish and/of east Texas because we have a ton of missing Texas heirs in old production. It’s very close to Shreveport and a lot of people buying minerals in the 1940ish time we’re from east Texas.
Next you indirect your names and look for a lease - if there is more than one you need to establish which is the holding lease. The easiest way to do this is to research production on sonris.
You can actually start with production and look for the lease on the WI side but it usually takes longer and is definitely a more complicated process.