Another been there done that and know your hell. Mine ran from upper New England to NYC with a girl 2 years younger than her but 10 years older in experience. My child had never been to NYC, had the street smarts of a puppy and the common sense of a flea. After she got mugged, she tried to turn herself into the first police officer she saw -- he was a security guard and not even remotely interested. It took her 14 hours to find a police station. Fortunately, all turned out well and at least she never ran again after that experience.
Kids ran from her Residential Treatment Center (RTC) on occasion. Two boys made it to Las Vegas. Most would get to "civilization" (a town with a population of about 500) and either call home, call a friend or call the Residential Treatment Center (RTC). The adventure of getting down a mountain in the wilderness was not their idea of fun.
Hope he turns around and comes back soon. As strange as it sounds, running can frequently turn into something positive, especially if the experience is bad enough to scare them but not bad enough to seriously harm them.
No matter what, though, I'm sorry you're going through this. HUGS