How can I revoke my power of attorney? What if my agent engages in unauthorized acts after the power of attorney has been revoked or terminated?

I've worked outside of the United States for the past 10 years. I granted my wife POA to purchase a home and access finances in 2004. We later divorced and I retained possession of the document. We've since remarried and reestablished a joint residence but because I was out of the country she oversaw the movement of my property into her home. When the question came up I was told that several documents including the POA had accidentally been misplaced or destroyed during the move. During my last visit, we moved once again into the house I own so she could sell hers. While checking online records of the sell of her house I discovered that the misplaced POA had been entered into county records at the same time.