I’ve had several bad experiences with bucks I’ve shot at last light and left overnight. If the meat didn’t flat out spoil, it sure tasted funky. I won’t leave a buck out now if the temperature is 40 degrees or above. And 40 is marginal, I believe you need the night air to dip down into the low 30s or cooler to have any hope of salvaging good, tasty meat from a deer that has lain on the ground, blood and guts in, for 12 hours or more.
This is the most agonizing dilemma that I hope you are not forced to deal with this season. But if you are, go back to your truck, relax for a few minutes and replay the shot in your mind. Where exactly did you hit the deer? What exact direction did he run off? Think and regroup. Then call a couple of experienced hunting buddies (no more than 2) and tell them to bring powerful lights.
Head out slowly, pick up the blood trail and try your best to find the deer. Grid search and look all night if you have to. Although you’ll constantly fret and worry as you search, most of the time you’ll find that deer and end up with a freezer full wonderful freezer meat to show for it.