My friend had a will which outlined her wishes. She also had designated her bank accounts (3) with 2 held jointly to her niece and one held jointly with me. All accounts had the joint account holder with survivorship. 5 1/2 days before she died her brother, who was neither on an account or executor of the will obtained POA. Two days before she died he had the account on which I was a joint owner closed, and moved to an account in her name with his name as POA. Now no one can touch the account except the estate. She had, in all probability, brain cancer and was heavily medicated and basically unable to respond when he shoved the documents in front of her. She could only make a mark while holding the pen. This change was totally against her wishes. What can be done?
But in any case. The point is that if the POA is proven to be invalid then nothing the brother did using it is legal. That's the part to focus on.
Can you afford legal advice? Is it worth it to you to contest the validity of the POA and the brother's subsequent activities?
As for the bank, go to the bank and speak with the Bank Manager. I'd be curious who signed for you to close the joint account. I would think your signature would be needed.
You can also make an appointment with an Elder Law Attorney see what he/she would recommend.