The records not available is not correct, proper. These records are permanent in nature. File RTI Application and seek whether those records are in permanent in nature, if destroyed as per existing norms, the date of such destruction, and copy of such entry disclosing this entry in destruction register, if they disappeared whether police complaint has been made as per law. Revenue dept are just avoiding to provide the records. Take it through RTI and what they exactly mean "non availability of records" as every authority continue to provide same information for all the records. Even if it is ancestral property, there should be some record as they may periodical survey, collect tax, prepare maps etc.
Contact a competent and sincere local advocate who may be having some links with revenue dept.and worked as Govt.Pleader.