I've decided to go for 100% completion in Dust: An Elysian Tail. So far everything's been going fairly smoothly.
There is, however, one exception. I seem to be missing a single item from a single room, and I am completely unable to find it. Here's the room in question, highlighted by a bright red circle:
This map is not my map. My map has the incomplete O in it.
I found the treasure chest easily enough, but it's still saying there's something here.
Where can I find my treasure?