By the way — I am not an attorney so take the above for what it is: The thoughts of an uninformed Mineral Owner. – nothing more
Actually you statements were very close to the mark. A probate may be needed. Possibly reopening a closed probate is an option. A heirship quiet title is also appropriate in some cases.
I was offered $7000.00/NMA from a contintental rep. The section is in 7N 5W. The two wells on the section pays over $5K/month from Continental. Maybe they are trying to squeeze those who did not handle their with holding taxes.