On the off chance he is on the AT. He will be alone, avoidant, and probably jittery based on previous reports. He is not likely to be wearing a mask if encountered unaware, but may put on a mask quickly for even a casual interaction. It may seem odd when he does it, particularly for a young person outdoors. I doubt he would camp right at a shelter, but rather choose a more hidden location. I don't think he's that experienced though to where he has practiced real stealth camping. He may think he is hidden but isn't. The picture that John B linked shows him by a stream which is probably a good bet on where to find him, or near a pond or lake. If he's moving around, he might be encountered at a water source. If he has a phone, he's going to be looking to charge it, probably in an overly secretive manner, furtive.
He had no money of his own, he was using her cards to get home. If his parents aided him, the authorities will be looking into as many records as they can. If they took more than a few grand out of the bank, the bank will flag that. If he is in the woods, he is going to run out of cash and food and winter is coming. He's from Florida and potentially has no winter hiking skills.
He could of course be in some other recreational area, wilderness, national forest. Or headed westward, he traveled around out west too. He knows how to hitchhike. Traveling around, he would have investigated many possible scenic and recreation areas all over. The longer he is out there, the more time he has to figure out a long term game plan.
Now if we knew what gear he had, we'd spot him a lot easier! I know some of you can name a pack at a hundred yards!