Rap, a high shoulder shot is just that; high shoulder. This shot usually always drops game in their tracks. Come down 4-6" from a high shoulder shot and it's a center shoulder shot; this sometimes drops them in their tracks. If it doesn't drop them, it's still heart arteries/lung shot. Come down another 4" and it's a low shoulder shot and centering the front of the heart/hearts main arteries. If it's a broad sided shot, come straight up the leg and the front of the heart and front portion of the lungs are behind the shoulder. This is why "l" like the shoulder shot; it's a high percentage shot. Broad side, behind the shoulder is also lung and back of the heart; quartering slightly away and it's heart/lung.

This is why I think it was a low leg hit; but I can't explain lung material found. I've never found bone on any shoulder shot I've done: high, center, or low. Lung material at the scene usually results in deer not to far; dead.

It's hard to diagnose a hit, not being there and seeing all the evidence left behind. I've been involved with a few trackings where bone was found and the deer wasn't retrieved. On some of the occasions, the deer were seen at later dates or on cameras with a broke front leg, but they survived.

Hope you find it, but don't let it get you down if you don't.