sounds like you either hit him where bobco19 stated, in 1 lung which are a bear to retrieve....i helped a buddy of mine track a 1 lung hit and we tracked it for 5 hrs before we found it still alive bedded in a cornfield. no telling how long it would have actually gone if we wouldn't have found it and finished it off...or your hit wasn't as good hieght wise as it appeared. you may have hit it high in the withers just above the lungs, in which case you'll probably see him next yr if he survives the shotgun season. either case, no ribbing here you've done everything you could to retrieve him. sorry man it happens. good luck