Money Lost at FNB

Hi. I am an FNB and Standard Bank Client. I was transferring money from my FNB Account to my Standard Bank Account and mistakenly entered a short account number. The transaction is supposed to have been unsuccessful and the money returned but FNB decided to direct the money to an unknown account number. They sent me to STD Bank but the consultant at STD Bank said they don't have such a client and account number. Please help me because this money was supposed to pay my House Bond.