Release of title deeds equitably mortgaged in education loan

My father has taken an education loan for my foreign studies in 2008 from the branch in which my father worked as assistant manager. This was returned to bank in full with interest in 2010. During this period (2008), my father was dismissed from the bank due to a bank fraud in his branch. His name was not in any FIR or so. The title deeds of the house I live in were mortgaged for education loan. They have not been returned. I was coborrower of the loan with my father. The title deeds mortgaged is in my mothers name. The title deeds file (which is with bank) has a printed page on its top which says that there was a bank fraud and that this title deed should not be given to my father. We went to the bank but they said that they cannot release title deeds and we should ask this in writing. We fear that bank may usurp our house as if we initiate return of title deeds. I want to get the title deeds back with NOCs and all. Now I am confused should I give this in writing to bank? Can bank claim our house in the name of fraud today or tomorrow? What are the options for recovering the title deeds from bank?