Lost Deposit Slip

Hi. Help please. Not sure what to do. I made a deposit but my passbook was not updated because the bank is offline. When I returned after a month and made a deposit transaction, my account was updated however it did not reflect the amount i previously made. I did not immediately called out my concern coz i wanted to check also my copy of deposit slip. And that's when i found out i most likely lost it. The following dat i went back to the bank to raise my concern. Its been 2weeks now and they haven't gave me a concrete update on my concern. I already told them that i cant find my deposit slip. They told me that they're still checking the cctv but then im having doubts if they're really doing it - the manager's response to me is quite inconsistent. What should i do please? Can i request a copy of the cctv footage? Does the request require legal process? Help me please. Thanks