In the junkyard cave area, how do I find the last piece to decipher the code? I found the two areas to rummage through, but after many attempts, no last piece. Also I created a blockage for the north east part of the map, but it seems to have gone away?
In the menu, under the heart, there is a quest log. The quest you're doing is 'Rat Problem', and you may be at the end of it for the time being so that's a good place to check (as it tells you when you hit the 'rest of the event is work in progress' point).
If not, that should suggest where to go next.