Do you have a copy/ full details of deposit receipt?If so find out whether any nomination had been registered.If such is the case the bank concerned would have paid the amount to the nominee on his claim as per extant procedure
Even if such payment was done, still the nominee is liable to the legal heirs and is required to act as a guardian in this matter and all lawful legal heirs are entitled to get their eligible share in it.
on the other hand,if there was no nomination,the bank is required to settle the amount by way of death claim to the legal heirs only.
You may approach the bank branch and get the full details as how the deposit receipt got discharged and then act accordingly. Should you find any problem/delay in getting the details,you may seek it under RTI Act.