I also think we need some consensus on what "failure" means. Some people call it failure when a bullet doesn't exit. Some consider it failure and wasted energy when it does exit. Some consider it failure if it doesn't retain all its weight. Some consider it failure if it doesn't fragment violently. Some people complain of bullet failure…after autopsying a dead animal killed by said bullet.
In regards to that hammer recovered from a black bear…it failed to perform as intended. HOWEVER…there's more to this story. The bullet is still very visibly deformed. There would be decently broad wounding from this kind of tumble. If the bear was found dead days later that might make sense. But if the bear only succumbed to its injury's days after being shot it's plainly indicative it wasn't shot in a very fatal spot to begin with.
Heck you could "ice pick" wound a bear or any other critter on this continent with a .308 FMJ load and if it was double lunged, heart shot, or hit in the liver there's no way it survives for days after. Hours maybe. MAYBE.