I agree with the 1 lung sentiment. It sounds like this will be a dead deer. Hopefully he laid down not far from where you last had blood and you'll be able to find him. Time is what he needs right now. Coyotes are few and far between here and a fox will do minimal damage. Give him time and you should be able to find him. I sent you a PM in case you want a hand looking.

As far as jumping the string goes, I videoed a hunt earlier this year where a buck came in feeding. He was perfectly calm and content. When the shot was taken it ended up being a spine shot at 22 yards. The hunter thought he had misjudged the distance, but when I was editing the video I looked at it frame by frame and the arrow was headed for just under center line in the chest. The deer ducked in the last 5 yards or so of flight and nearly got under the arrow.

You can never know when a deer is going to jump the string, and it's amazing how quick they are when they do.