Looking Up Lease Copy

Hello, we are receiving royalties from Prima Exploration in 25N-58E-S13 from an old vertical well, and I have learned that they have permitted 4 horizontal wells in the same section. Unfortunately we do not have a copy of the lease for this as it was not in my late mother’s papers. I contacted Prima about the proposed wells, and they said they planned to drill them this year. I also inquired about getting a copy of the lease, and they said they could not provide one, as this was part of a unit, and they did not know which lease I might be on…so I am wondering how difficult it would be to go to Richland Co Courthouse and try to get a copy from there? Anyone who may have done this please advise if it is even possible, as I’d like to try and determine if we will be entitled to any upcoming royalties from the new wells… Thanks, Mark Presley