I just encountered some strange behaviour ingame. After the tutorial, you arrive in the old graveyard with some monster standing in the middle. The monster had a point of interest interrogation mark on it, I left to look for other stuff on the map and when I came back a few minutes later, the interrogation mark had disappear and I could not activate the puzzle anymore. Is there any sort of time limit after discovering some POI to clean them? Or is it some glitch? Or maybe I missed some information.