If the oring started in front of those little wings, there is no way possible the BH did not open. Can I accound for the lack of anything on the BH? Maybe it wiped off coming out. Maybe the shot barely caught the hide and not the vitals. Meaning the BH opened mostly as it was exiting the yote. And the fletching hung in a bit longer or he was bleeding more my the time the fletch got to the wound.

I would think the shot was less than a perfect shot. You didn't find him after all. High or low just barely going through the hide the arrow may have been exiting before it was able to fully open. Then it had slowed enoung for the fletch to hang up a second and it closed the blades back and bloodied the fltech.

Thats my guess anyway.