As title says, I tried to go down the shelter basement after just spawning into the (new) world and a message saying something like “The way down is blocked”. After that the area map (the one accessed by M) displayed everything as unexplored. Saving the game didn’t create any files, just an empty Save dir.
Also, in a new game created just after that the NPC at the shelter gave me gasoline (200) as reward, without a container. So right now I somehow have 200 gasoline stored somewhere on me (and I REALLY don’t want to know where it’s stored).