Sorry to hear the news of your elk. You sound genuine, honest, and have put yourself out there in hopes of bettering your chances of recovering your elk. That takes courage. I hope you or friends will have another opportunity to look again.
Don't overthink it. Vitals are vitals and avoiding bone isn't a bad thing. Plan on one well-executed shot. If you have any doubts, don't shoot. Only shoot when you are 100% confident in your ability to deliver the bullet into the vitals. If you put a sharp stick through both lungs, an elk will only be alive a matter of seconds. Same for a bullet plus you'll be delivering a serious load of energy in the form of hydrostatic shock. Hitting bone obviously causes more damage but isn't required. Heart/lung vital hits kill animals in seconds regardless of weapon choice.
I sense you've lost a lot of confidence over this, but I hope that's not the case. You're seasoned given your years of experience. Hunting will always have the potential of sad endings, which must be examined and sorted out. They are the consequence of the hunter or the animal or possibly both. Was the shot rushed? Did the animal move? Etc., etc., etc... Something caused a poorly placed arrow, bullet, or slug.
I feel the best medicine for your own conscience - assuming a high standard of ethics - is examining the shot and whether or not you'd take it again. If the answer is "yes, I'd take that shot again", then you can do your best to recover the animal with your chin held high. If the answer is "no, I knew I shouldn't have taken that shot", then you have the opportunity to learn and grow, while doing your best to recover the animal. I don't think anyone who takes hunting seriously ever stops learning and calibrating their own set of ethical standards. By definition, hunting is, in part, about killing. Striving for quick, humane kills is and should be the goal. I have no doubt that was your goal.
