I'm thinking it had to have hit something downrange. The forces on the shaft are greatest as it overcomes inertia upon release (at the bow). If it survived that then the stresses only got less on it as it went downrange, unless it hit something... anything. It wouldn't take much. I have seen arrows blow up on release that travelled downrange (and even had parts embed in a target at 40 yards). Any chance that it blew up when you released it and that it scattered from there? In any case, glad to hear that you're alright. A/C's next year?