Letting it set a few hours is the best advice. The problem with a sholder hit is they do not want to bed down right away and stay down as it hurts them. On the flip side, its my experiance that they do not travel far because it is hard for them too walk too. They seem to bed often and get up right away, but there will not be much blood obviously. Let them set and if you got the lungs(hopefully both but maybe only one with 4 inches of penitration you should find him within 300 yards in the morning. Was there blood up the arrow? It may have broken off inside the animal and you have a deeper hit than you think.