The Bank Examiner Scheme -

If a stranger tells you that he or she is an examiner or investigator and
asks you to help catch a dishonest employee, BEWARE. If you seem interested,
the con artist will say he or she will re-deposit your money in such a way that
the "dishonest" teller will be caught red-handed. The phony examiner will pick up
your money and give you a fake receipt, never to be seen or heard from again.
A simple preventative measure would be to call and check with your financial institution before doing anything. Banks never involve their account holders in investigations.