Regardless,
QFT
I don't think that premium hunting ammo for big game is so expensive, all things considered (how many times do we plan on missing, right). This is especially true if paying to hunt on private land. If only hunting once a year with it and using FMJ for off season fun, expensive hunting ammo is still relatively cheap per pound of whitetail. IIRC, I pay ~$170 for the out of state license in WV (where my family is) to have the opportunity of one antlered and one antlerless deer. So even at $3/round for the premium hunting ammo, it's a tiny addition to the cost per pound on a whitetail. Heck, even at $5/rd, it's a pretty cheap price for the whole animal.
Although I'm generally a proponent of smaller and faster, there's no reason any of the cartridges you downplay won't work well given proper bullet selection. Hell, bullet selection is not even that hard for the .350 and especially the .450. When you push a bullet designed for normal handgun velocities over 2000 fps, then lack of expansion is not going to be a common problem. In any case, failure to find a deer shot through and through is primarily either a failure in shot placement or a failure in tracking regardless of bullet performance.
Availability of .243 ammo is far less of a problem than availability of quality .243 hunting ammo. Most commonly available .243 ammo is not suitable for hunting deer.
I hope he actually looked for the deer instead of just assuming that he missed since they ran off. I'm not sure why but a lot of people seem to have the idea that any deer shot with a rifle should immediately drop, even though it is very rare for a deer to drop immediately without a CNS hit.
