Standard bank atm took our money and won't refund us!

My husband went to deposit money at the Windermere Standard Bank atm on the 24th December 2019. R350 got sucked in the atm and disappeared. He immediately went into the bank, who said they will rectify and refund him. He has followed up numerous times, and went in to the bank this morning to be told they cannot find the funds? How is that possible? This is the 2nd time this has happened at this branch in 2019. Who is being held responsible as clearly if they cannot locate the funds that means someone inside has taken the cash! It's no wonder Standard Bank branches are closing all over. Will take our business elsewhere.