Bank Statements Enquiry

Hey I have recently complained about my grandfather not being able to get his bank statements from FNB of the year 2002. We requested the statements because they are are amounts of money that are unaccounted for. FNB said that they investigated our case and they could not find the bank statements and they also mentioned that even if they found them they could not release them because they were from 20 years ago. This came as a surprise because they had previously gave us bank statements from February to mid July of the same year. The only statements that are missing are from mid July to October.