I'm sure he didn't think about having to worry about an aerial scan for him, but I doubt he was completely disconnected from all people for seventeen years. For one thing, they didn't specify how he was getting food. It is theoretically possible that he hunted for it and that's it, but given the difficulty in doing this in an area near a large Chinese city and maintaining sufficient nutrition to stay healthy, it's probable that he had another mechanism such as entering a nearby location to purchase or steal food. So he could probably have learned of the existence of drones. If he had thought police would have used them to find him, he could have disguised his location or simply moved to another place, as the police could only find him after having a good enough idea that he was to be found in the mountains there. And that's another point that makes it less likely that he never saw a person for that time, as the police had to learn this possibility from somebody.