JMR40,
As Huntnshoot already noted, that was a TSX, not a Tipped TSX, and it did open even thought the animal was shot at much longer range than the mule deer (though with a little faster cartridge). Barnes BC's for TSX's, in particular, are a little high, one reason for the introduction of the Tipped TSX.
The other reason (or at least my guess about another reason) is that some TSX's don't open much, if at all, though that isn't the case with the one in the photo. I've seen over 100 animals taken with the original Barnes X, TSX's and Tipped TSX's, including a bunch my wife and I have shot. The hollow-point version sometimes (rarely) fails to expand, usually in calibers from .24 to .30. One of the guesses as to why is the hollow-point sometimes gets battered partly or completely closed due to recoil while in the magazine. This is why it doesn't happen (or at least I haven't seen or heard of it happening) with .22 caliber or over-.30 caliber TSX's: The recoil too's light in .22 centerfires, and the hollow-point is a lot bigger in bullets over .30 caliber.
But I have yet to see this in Tipped TSX's, probably because the tip increases BC, but more importantly because there's a huge hollow-point where the plastic tip is inserted into the bullet. Have heard of one instance where a TTSX didn't expand, apparently because it hit a bone at an angle, bending the tip over, but so far I haven't seen it happen. Also haven't seen it happen with Nosler E-Tips or Hornady GMX's, which are of similar design, and plenty of all three have been shot into various animals at distances where velocity had fallen to down around 2000 fps.
Maybe the bullet didn't open--but I doubt it. It looks to me like shot placement was the big factor. Hits around the edges of the lungs with bullets that don't send off any fragments just don't kill all that quickly.
