TUPPER LAKE, N.Y. — In the early hours of a winter morning here more than two years ago, Colin Gillis vanished.

He had returned on a break from his freshman year in college to the place he had grown up. Set in the foothills of several regional peaks, about 20 miles west of Saranac Lake, Tupper Lake is a six-traffic-light logging town turned recreation hot spot, a hamlet of about 6,000 where children and teenagers roam freely.

Under a clear cold sky and a nearly full moon, Mr. Gillis, 18 at the time, was last seen wandering down a road that winds through the verdant mountains and rushing rivers of Adirondack Park. All that was ever found were his driver’s license and a tobacco pipe.

It is not uncommon for people to go missing in the park, which sprawls over 9,375 square miles, almost the size of Lake Erie. Park rangers conducted 506 search missions from 2011 through 2013 for people who were lost or overdue at their destinations, according to annual reports. Rescue missions for people who were injured, stricken ill or otherwise physically immobile were conducted with similar frequency. In that span, 28 bodies were recovered — fatalities from drowning, falling, hypothermia or natural causes such as heart attacks.