Land allotted during India partition

Dear Respected Attorneys, My grand father migrated from Pakistan to India during 1947 unfortunate partition. They had more than 4 acre land in Pakistan and were supposed to get land in India by Rehab department,. At around 1959 year compensation application was filed by my Grandfather but it was rejected by the Asst. Settlement Comissioner of Govt of India ,Ministry of Rehalibation on the ground that rural land allotment already stands on my grandfather name but when they went to Patwari of the concerned area around 2005 year where the land was allocated , Patwari reported that no land has been allocated to then nor any entry in the Mal record of Jamabandi has been found . My Question is, what's the best legal way we could claim our land and what are the bottlenecks we should be aware of? Since that land was allotted in 1947 we still don't know where that land is and how to claim is, so if someone else might have been living or occupied that land since then, what are our options to get that land or some other land from the government?