Believe it. Once the time-lock is engaged, the vault cannot be opened by any method short of physical force, which is why they had to call a locksmith - any "back-door" method of opening the vault would defeat the purpose of the time-lock. And the fact that this locksmith came all the way from Ohio to Williamsburg, PA says to me that they had to call a locksmith with some fairly specialized knowledge of bank vaults, and not just the guy who jimmys your car when you lock the keys inside. ;)
However, you're probably right that the manager bears a great deal of responsibility here. Typically, in most bank branches, the vault is kept open during the day, to allow for easy access, and isn't closed and locked until the end of the day. But that means that someone allowed the vault door to close without first insuring that the vault didn't have anyone in it. Which would usually be the responsibility of the manager or assistant manager.
Bankers are pigs for time and devotion, and don't pay squat.
As a former bank employee, I couldn't agree more ;)