Some part of our Land is missing as we did not Mutate for 43 years.

Dear sir, My grandmother bought 4 acres of land in 1977 and registered it but did not perform mutation. she has 2 sons and three daughters. After marriage, they all got dispersed. In 2017 she died. Then all the 5 got to know about the 4 acres land. They went to SRO and brought the encumbrance certificate and in that it is clearly mentioned 4 acres. But when we searched in ilrms/gis and checked the ROR table, on the previous owner(Seller) Name, there was only 2 acres land. It is not showing another 2 acres of land. Now what to do sir? we want to mutate but there is only 2 acres of land.