The estate plan is still valid and you can continue to use the durable power of attorney. The lawyer's standing with the bar, while unfortunate, has no effect on the validity of your mother's estate plan. The creditor's request for documentation of the power of attorney's continued validity is undoubtedly a violation of your state's law. The creditor should permit you to certify that to the best of your knowledge your mother has not revoked the document without providing documentation.