Just because you think you lost blood doesn't mean there isn't a trail to go off of. Make some circles or some zig zag searches. Look on the underside of stuff.
I agree four hours and give up ? Also I would be looking for a deer track with the deer walking with it's toes spread. An old timer informed me of
that. He said that a wounded deer will walk with it's toes spread for balance. Any ways I am sorry to here about your luck.