If you have purchased the same in court auction, you are an innocent buyer. Unless the power of attorney stipulations are studied, it is difficult to comment as your version is that POA is meant for conversion and development and not for sale. In what capacity the bank sold the property, and whether the wife is a guarantor with her husband etc., is not known.
Contact a local advocate. File an application to the Bank and seek the Legal opinion on record on that property. They must provide it to you. The bank sold it to you in an auction and the presumption is POA is in no way connected with such sale, and the property was mortgaged to the Bank as security by real owners only.