Dear Mr.Rao,
Your presumptions are exactly correct and the final question following your astonishment is apt. As far as I know, for any theft of Bank's money kept in the ATM by burglary, the concerned employees of the Bank would not be proceeded against. Normally group pf ATMs would be under the scrutiny of a monitoring system and only the employees in charge will have access to the monitoring system to watch the entire transactions through such every ATM and load them with currency as and when required. Therefore, if short fall in cash in between successive ATM replenishment is noticed then normally the employees concerned would be held responsible for they alone would have the key for the machines and know the passwords if outside agencies are not engaged for such work. Though the single key was with the cashier and the questioner, as admitted by himself, was not present at the time of the particular successive replenishment of currency, he, as the Head Cashier, can not disown his joint responsibility for the monetary loss. Moreover, the short fall in cash might have been detected by the Manager and hence his suspension might be. Based on such presumable facts only, I gave my reply as above.