Wife missing complaint filed how can we claim FDs in wife's name

My wife is diagnosed with stage 4 stomach cancer.She was done with her surgery her chemotherapy was going on.Thinking that she is creating problem for us,she left home.Its been more than 2 months but still we are not able to find her.She have some fds in financial institutions(pathpedi).Nominee is my son.Also he is joint account holder with her (savings a/c).Fds are already matured.As we were busy in searching her,I went after 1 month.They are telling You can't withdraw money,they require my wife signs.What all options do I have?We have already filed missing complaint.Can seven year period for missing person can be challenged as she is advanced stomach cancer patient?