If that happens again, pull off a yard of line and throw a loop downstream. Once the fish feels the pressure coming from behind it might move him. Or you could simply get out of the water and get downstream from the fish. Once you pull his head downstream he should react. Sometimes big Atlantic Salmon do the sulky thing. You get the normal long slow pull on the fly and raise into him, and he just sits there like hes trying to figure out whats happening. Another old Gillie trick is to thread a ring onto the line and let it travel down to his nose, apparently the annoyance of something hitting him on the snout might send him into a frenzy. I came across a guy one early morning standing in the river with a big fish on. It was a standoff. Both fish and Angler stood their ground for about 20 minutes until the guy gave some slack and the fish moved out of his sulking hole.