It's entirely possible that the bullet stayed together and came out unnoticed as I was gutting the elk. I wasn't really searching for it at the time, just sort of half-way watching for it.
So the bullet may have performed as advertised, but it certainly didn't exit the other side. It did kill the elk with one shot, so I can't complain. I just expected it to pass through at that close range.
I appreciate everyone's input. Thanks!
Edit: Interesting article on bullet performance
here.