if there is not a blood trail it maybe all in the chest cavity, you sound pretty sure you hit it good, if its hit good and is dying it'll proberly take the easyest way out of there. If it was on a deer trail I'd follow it and look to the sides of it. it's gonna go to where it feels safe and use familar routes, or easy routes I get alot of practice at this because mine dont like to stay put after I shoot them