Yeah I was wondering what that Gunblade noise was also. This theory does make a lot of sense though. Maybe he was on the verge of dying but Rinoa was looking for him, and remember how the white feather appeared after she held her necklace? She was sending him a sign that she was thinking about him and it gave Squall hope, which probably kept him alive. Then he appeared in the field where he and Rinoa promised to meet. I think she still had her powers, so I’m guessing she sort of “summoned” him to appear at that place.