If the POA paperwork was indeed invalid, then the advisor had no right to move the funds. A lawyer could help pursue this.
A lawyer might take this on contingency if it’s a strong case.
Try reporting this to the CA Department of Justice’s elder abuse division: Division of Medi-Cal Fraud & Elder Abuse | State of California - Department of Justice - Office of the Attorney General. They’re usually very interested in these kinds of cases.
This is definitely something for a lawyer.