Is that reddish areas fire caulking? If so, I havent seen it used on horizontal penetrations.
Maybe you could access through the missing KO
Yes, the red stuff is fire caulk...this was a hallway, with double layers of sheetrock.
Of course, having a j-box in the middle of the wall raises all sorts of other issues....
As luck would have it, in the course of sorting out the wiring, this j-box was eventually completely abandoned.