Check your divorce papers first. If you file a report claiming that the vehicle is stolen, you yourself can get in trouble. Your divorce papers should state who was awarded what property. If that particular vehicle is in it, listed as hers, then she must change ownership. Unless is is financed still. In either case, your best bet is to check with your attorney and have your divorce decree with you and any or all settlement agreements. If the vehicle was awarded to your ex in the papers, you can petition the courts in your state/county to force her to change ownership and get her for contempt. If the vehicle is not in the divorce papers, use the courts to get the vehicle back. It makes you look better if it turns into a legal battle.