There was an interesting incident that happened a long time ago (maybe 10-15 years) in the Emigrant Wilderness. One hiker was on leave from the Marines, so obviously he was not some complete fool in the outdoors. He went on a solo day hike, so he didn't have a lot of gear with him, probably only a jacket, a water bottle, and a snack. After he got ten miles from the trailhead, somehow he fell off the trail and then slid and fell down into a creek bed. In the fall, he sustained two broken legs. Somehow he kept his wits about him, and he remembered bits and pieces of his military training. He built a "squirrel's nest" out of dead leaves, and that was his only shelter at night. He drank from the creek. Somehow, the searchers did not find him, partly because they had no idea where to look other than the trailhead where his car was parked. They had covered that trail, but they did not search the creek bed. Anyway, after a week or so, the search was called off. The Marine kept enough strength after two or three weeks to crawl back up the hill and to crawl back out the trail. He was found, taken to the hospital, and finally recovered.
The moral of the story is that even though bad things don't happen very often, it seems like they will hit when you are least prepared for it. Remember the whistle, which would have helped the Marine.