What probably happened is a teller sold money (20's') to the vault and the vault sold it to the ATM . He or she probably put a 50 in with their 20's in error and their drawer will probably show up short $30. today when the main vault balances her work. Really hard to trace but they could put 2 and 2 together if she remembered selling money to the ATM. The ATM won't show a shortage because it goes by bill counts not dollar amounts. It could have been a $1.00 bill and still balanced. You would have called then wouldn't you...
A lot of times on a busy weekend the vault runs short and buys money from the tellers if they have the extra.Then the vault would resell it to other tellers or to the ATM if it needs filling. If the armoured car (with cash shipment) doesn't come till later in the day they get desperate to fill the ATM's.
If they had filled it with 50's instead of 20's you would have got more than one.
The other option is if a outside firm handles the ATM's..they will eat the loss.
They will probably just write it off. Having been such a busy weekend they won't want to take the time to look at every withdrawl over the holiday weekend. They would be there forever making phone calls and asking "Did you get too much money?"
Snoozy...Former Bank worker.