Sure, but its a -lot- easier to prove that John Smith working at the bank got your PIN and made a withdraw of $XXX on X day.
Even if you have good reason to believe John Smith knows your PIN, proving it is going to be next to impossible.
First you have to persuade the bank that someone else knows your PIN through no fault of your own. How do you prove this to the satisfaction of a huge organisation which is set up at every level to assume that this is physically impossible?
Next you have to convince them that not only did someone else find your PIN, that someone was one of their staff. As opposed to, say, the postman who's on a low wage and sees credit cards and PINs in his bag every day.
Next you have to persuade them to do one of the following:
- Admit that their systems are not perfect - there is a possibility that John Smith could indeed have got the PIN.
- Give you sufficient access to determine this for yourself.
Next you have to get somebody sufficiently high-up in the bank to read what you have to say and take it seriously. Though by this point the bank has already either refunded your money or asked the police to investigate what they perceive as you attempting to defraud them of the money.