At the distance the shot was fired, the shot was a near solid mass when it struck the bear. I have no doubt that it would penetrate a bears skull at that range. I used to know an old farmer here who killed his domestic hogs with a .410 with bird shot. From a couple of feet away, the little .410 worked fine, every time. Certainly wouldn’t be my first choice to stop a bear though....
Even if there’s no skull penetration, I would think there’s still a significant concussive effect with might stun the animal long enough to get you out of there