I think this highlights the difference between survival kit and being properly equipped in my mind. On a day hike, being properly equipped might mean having a survival bag (or whatever) in your rucksack in case of a problem. The survival kit is what you have when you lose your bag.

Losing the majority of your kit is a rarity, and I think the most likely situations are covered here already.

I would point out that a lot of our survival planning seems to assume we are mobile. If we lose that mobility you don't need to be very far away from your kit to not be able to reach it - a relative of mine broke her leg badly by slipping on some wet grass a few years back - happily there were passers by to help her, but she struggled to cover any distance before they got to her. In the dark and wet....I think a whistle, light and space blanket might make all the difference in your pocket