I used to work in a group home for mentally challenged folks. We had one adult male in his late 20's who was a "runner." By that, I mean he would slip out of the house sometimes and end up a mile or two away from the home. He was well known to the local PD because we were instructed that anytime we noticed him gone, we were to call them. A BOLO would go out immediately and whatever patrol was in the general area would drive around looking for him. Once he was found in a big supermarket, another time when he was at the work center, he ended up in the woods behind it. I think the longest time he was missing was 6 or 8 hours but it was nearly always LE who found him.
My point is, since Johnny is not a resident of that city, it's possible that the local cops are just not 100% focused on trying to find him, as if he lived there and they knew him. They do work with LE in other cities and states, but it's hard to really search for a person if they're not familiar with him, his habits, his mannerisms, even his gait. Even though they have a general description of him, his appearance could have changed drastically. Even the way he normally walks may have changed... he's tired, he may be hungry, he is confused, disoriented... he is not going to look or act the same.
Some things to think about.