Frowned upon in some jurisdictions depending on how the aftermath plays out...
http://www.gamewarden.ab.ca/agwmagazine/1998/winter%201998/archns13.htm
That's a bit different. Witnesses watched him make a shot at 75 yards, miss and give up. Yeah, I'd call that abandonment.
To share my own story, somehow, in all my years hunting, I'd never lost one until this season. And I've lost 2- a buck and a doe. In the case of the buck, I pushed him too hard too fast, could see him more than once but didn't have a clear enough shot to finish him, so I tracked him until the terrain got too rough to continue alone- went home, got 2 helpers and returned, picked up the trail and he beat us, fair and square. Made his way into a swamp and we couldn't follow.
The second was a doe. She jumped, was clearly hit, ran to a treeline. We followed in, I had the only headlamp between us and neither kept our packs with us as the first blood puddle in the snow led us to think she didn't go far. 3 hours and a couple of sightings later of her, still following blood trail and tracks, I called it off until daylight the next day as we still had to get back to our machine and camp. 4 of us went out the next day, picked up the trail and after an hour and a half, spotted her once- as she BOUNDED away, still leaving drops of blood but clearly not either a gut shot or a kill shot. I called it off, and while I regret wounding an animal, she was clearly not going to die from it, and was going to lead another merry chase. I felt like we were not going to be able to keep up to her to get a second shot, she was urinating and crapping normally, had bedded down once or twice according to the trail, and two of us were still physically spent from the night prior.
It happens- but I believe if you've gone as far as you can, done as much as you or your party is capable of, you've done your part. It's why it's called hunting, not killing.