It would be helpful to know what bullet your friend was using. I had something similar happen several years ago. I shot a small buck (120lb live weight) in the point of the shoulder with an early 90's vintage 100gr ballistic tip out of a .250 Sav.
The bullet came apart after breaking the shoulder bone and never entered the chest cavity. This deer was being pushed by hounds and they were able to bay him in a thicket a couple of hundred yards from where he was shot, or I would not have recovered him.
He would have most likely survived the wound, but probably never regained the used of the leg.
It sounds like this may be what happened with your friend's deer.
Had a similar event. Bullet raked the shoulder and exited. Was seen the next day a mile away feeding on corn. Survived that season, taken the next season, had a slight limp.
