Quoting Kampy
it could of course be because its outside the skybox, but the other displacements that can be seen on the picture are outside as well and I believe Ive seen it inside somewhere too although Im not sure.
Sorry man, I don't get it. You didn't seriously put this outside the map? If you did, the problem is so obvious, the question sounds a little funny...
Do you mean it is inside the skybox? Like, outside the map itself but inside the "sky_camera" area of the 3D skybox? If so, it is probably hidden by vis. Note that brushes with the "skybox" or "nodraw" texture can block visibility while still being fully transparent. This can result in odd cuts and disappearances.
Nevertheless, I'm confused...