Its unfortunate, but sooner or later, gun or bow, something like this is going to happen. Don't let it get you down, you are doing a good job continuing the search. As for survival, we'd have to know the exact hit. If it is not hit in a vital area and infection does not set in, there is a decent chance the buck will make it. Actually hitting bone could lessen his chances. As I said, a lot depends on where and what was hit. Keep looking, especially if there is water nearby. Wounded deer often head for water and you could likely find him in or near the water. Good luck!