A little about success rate on tracking other people's deer..... its not about you or the dog's success rate, but about the hunter's. I've found if you take every call hunters as a whole tend to be "optimistic" to put it lightly about their own ability and the hit on the animal. You'll do good to find 30% of all cold calls.
That said, in 8 years we have only had 2 folks find the deer later, and one was submerged in a river under a log that the dog took us to, just couldn't see it at night. The vast majority of calls turn out to be non-fatally hit deer. If I had a dollar for every time I've heard "I ten-ringed him, that's right where my sight pin was" I could pay for lots of dog food.
On deer hit by myself, family, and people I trust to know what a fatal shot looks like we are near 100% recovery on deer described as fatal wounds. I have full faith that if the deer is dead we'll find it.
As a tracker your biggest hurdle is the average (clueless) hunter...... oh we have stories!
R