RE: My first Bow Hunting experience
I prefer to use fixed blades as well (Thunderhead 125). NOTHING stops these....not even the shoulder bone. Maybe it is my bow...or the weight of arrow that I am shooting...but these things will go through anything.
As for how tough deer are....
My friend is a taxidermist. He arrowed a deer last year and proceeed to prepare the head...He found a slug in the front of the buck's throat against the skin. It had come through the deer from around the shoulder area a year or so before. It was completely healed. The only reason the slug was recovered is because he was doing the mount.
So, if you did have a poor shoulder shot.....the deer might live. I wouldn't stop looking for it just yet.