This news story is playing on my mind.
www.bbc.co.uk/news/uk-scotland-tayside-central-54732781
In these cases it is usually an inexperienced or ill-prepared walker but this man was super experienced GB level.
One thing puzzling me, do they not have a garmin location trace or similar? I do not know many runners, especially serious ones, that run “tech naked”. Do you always trace your runs?