Keep looking UNTIL there is NO possibility of finding the animal you shoot. I have regretably had to GIVE UP on a couple of occasions and it makes me very sick at my stomach. Usually have a very hard time sleeping after it happens, playing it over and over in my mind. I still can't figure out one from 3 years ago. Good shot, I thought, good bright blood, pass through, good trail for 100 yards, then small drops, then nothing. Looked from 4:00 in the evening til about 10:30, then again for about 4 hours the next morning. No idea where that deer ended up. Congrats on your find. Hopefully your friend learned a valuable lesson.
BOB