bank teller incompetence

Im sorry for bringing such a trivial matter to you.. This has been a problem for me for decades.. I own a small buisinees which requires me to deposit large amounts of cash once in while.. Today i sent my son to make a 3400 dollar deposit, the teller turned and walked away and returned to count the money, it is unclear why the money was removed from my sones view. I called the operations managaegr of the banks and it was of course my fault for my son not asking for a teller that worked at that set of teller stations?.. What whould have happened if the teller rutuned and 500 dollars or more, was missing? All was accountd for at this deposit.. According to the bank if the tills were on at the end of the day i of course was wrong.. Ive had money dissappear at this bank on other occations and it usually turns up, once under a magazine two days later!! What whould a judge rule in this case if i took it to small claims court?.. Thanks dave