"Pat downs" without an arrest are only permitted when a police officer has articulable suspicion that a crime is or is about to be committed and the "pat down" is limited to items that pose a danger to others such as weapons. Without reading the officer's report or hearing his basis for stopping your son it is difficult to know if the officer acted lawfully or not.
Review the facts with a local criminal defnse attorney for advice. In general, a police officer can conduct a :pat down" search under certain circumstances. This includes a minor without you being present. These facts are questionable. www.kacdl.net
I am trying to give you a general answer to your question. We do not have an attorney-client relationship by this response on the avvo website. I have not been retained to represent you. I am licensed to practice law in Kentucky and in federal court in this state and the Southern District of Indiana. You need to seek legal advice from an attorney licensed to practice in your area..