Mary,

The person in the bank who said that they could not return the funds is either very new to the field, lying or referring to something else.

The "reversibility" is exactly what the scammers are using for this kind of scams. A check is deposited, credited and later reversed.

What the bank can not do is make the book entry/operation disappear. They must reverse it with a new book entry and, if it is the case, another operation such as a return wire transfer, for example.

Take care,
Luiz

PS: In case anyone is wondering why I feel confident to write about this issue, it's because I worked as head of treasury and financial markets for a huge Dutch banks in a country where frauds and scams are a major concern.