I did notice that when I went to try edit the apartment again just a little bit ago. The wall covering was missing from the outer wall where the windows are. I figured it disappeared because I deleted the wall behind the planter box.
With not being able to edit the outer wall, as it's out of bounds, we can't put the wall covering back on.
Now that I am thinking more about it, I remember talk about that sort of thing, back when City Living first came out.