I don't think a neck shot that fails to hit the spine is a very good index of bullet performance, and it certainly isn't a sufficient measure of performance for praise or condemnation of either the bullet or it's cartridge. The old X bullet that many claimed expanded irregularly, expanded to nearly an inch, after penetrating 32" of my buffalo, yet the impact velocity was only 2000 fps. So bullet performance relates not only to impact velocity, but also to target density. There is little fluid bearing tissue in a deer's neck, the catalyst for X bullet expansion, to produce optimum expansion. A pal of mine swears by the 140 gr TTSX loaded to 2900 in his (formally my) Brno 600 7X57 for moose, and he has a bunch of recovered bullets that Barnes could use in their adds to illustrate textbook performance. Those moose, for the most part, were found where they had stood. Now, would a Partition have anchored the deer with the same shot? Perhaps, if the forward section of the bullet expanded rapidly enough to shock the spinal cord, but its by no means a sure thing, that would work every time.
That aside, congratulations to both father and son for having the fortitude successfully make the followup despite the difficult and challenging conditions. Many hunters would have written that one off long before 3 hours had elapsed. That speaks highly of your character. #2 earned that one, and likely learned a thing or two about bullet placement and tracking, so all in all, the experience was valuable.