Pleaselog inorregisterto add a comment.
There is no item in the game that is impossible to get to.I just answered your question, but I figure that you will want to know how to get to the item too.I am doing this from my phone so I can’t circle things for you, but I will explain.
I think that the item that you are talking about is item Q(Silver Powder), as there are stairs leading up to it, which can be visible. Other possibilities are items M and N, but I find this unlikely as they can be accessed easily.
So, to get to the Silver Powder, follow these steps(Note that it requires Surf):
You probably could have done it yourself with the map, but meh.
Hope I helped.