If you truly felt it was a shot too far back, then I say you made the right call to back out until morning. It sucks that it ended this way, but you could have just as easily bumped him onto property you couldn't hunt.
If I ever think I have a liver or gut shot critter on my hands, I back out and come back that afternoon or next morning, taking my chances with the coyotes. If I know I had a solid shot then I go right in.
From what I can tell, you made the right choice for the info you had.
