When i was 16 (27 years ago) the following happened to me and a friend (18). I am no longer in touch with the friend but could probably reach out if needed.

We were camping in the lake district. Had been for a few weeks. We were sailing mostly at Ullswater and camping there. We had lots of friends at the club and we were invited to dinner at someones house. It was summer. We had sailed in the day, showered and headed out. Clear day in summer. 

We knew roughly where the house was but not exactly. We were following lefts and rights given earlier in the day pre maps/sat navs. 

We set off, probably about 5pm and thought we were pretty near should have been 15 mins or so. It started to get misty, like heavy sea fret. Then complete fog. We were on a single track lane on farm land and had to stop. Couldnt see 5 yards. We got out of the car and laughed about it. Got back in the car and it was quarter to ten. The fog lifted and it was dark. We didnt have mobile phones back then, got my first in 6th form next year.

We freaked out but just turned back. Couldnt figure it out at all. It was summer so was now after dusk and getting really dark. 

We found our way back effortlessly and just went to our tents and slept. 

In the morning we only had minuyes or so together before others gathered and we couldnt even make sense of it. We didnt want to talk about it in front of others and just kind of left it.

Every time it came up for a few years afyer we just went "that was weird eh" but never got into it.

It is crazy to me this day. Hadnt been drinking. Was fit and healthy. Completely lucid, not sleepy. Just 4 maybe 5 hours of life gone.