I'm pretty sure that's covered by 'unlucky': it's not the sort of thing that should give any reasonably prepared hiker cause for considering abandoning the practice as too risky. And 'all the time' is a considerable exaggeration when we consider how many times people set off on a hike in any given year.
Here's a random example from the top of my head.
http://www.nzherald.co.nz/world/news/article.cfm?c_id=2&obje...
tl;dr woman who had walked the Appalachian trail multiple times leaves the trail to pee, never finds her way back to the trail.