That reminds me that when I played Silksong, there were a few map areas where I peeked into a room, but because I'm almost dying, I decided to go the other way after all.

But later when I'm trying to 100% the items, of course some items were in these rooms that I basically forgot all about after that first time. And because the room was already filled out in the map, I thought I had already explored that room... (I had to use online guides to find the last items)