At the shot, the bear dropped and I was starting to celebrate in my head. A second or 2 later, it got up and took off. It ran away fast and back into the thicket.
Almost certainly hit the spinous process above the spine. You didn't say what grain NBT, however all of them will go through a black bear shoulder. What you described is what happens when you hit high and go above the spine- i.e. momentary paralysis and then they recover.
