Typically, the trail markers are piles of rocks called “carins”. They aren’t temporary things that a hiking group leaves behind like breadcrumbs. On a hike above treeline, there isn’t necessarily a well-worn path to follow. It’s often just walking across a bare surface. The carins are used to let hikers know the path to follow. But it can be easy to miss them. If this was a novice hiker or he just overlooked one of the carins, it would be easy to go off trail.