I've read recently that many have found 1/2 arrows while tracking a deer. This happened to me last year and I wonder what causes it. I have an idea, but it may be wrong.
As a deer runs through thick cover, the arrow hits a tree and breaks. It spins off at tremendous velocity and can go quite some distance. In addition, unless you are looking closely, a section of arrow is quite easy to miss.
It doesn't happen asmuch as it use to because today's bows propel the arrows so much faster, most shots are pass throughs.
UI found this half this morning, the rest was still in the deer. That is slightly unusual.