hey these things happen. don't beat yourself up over it, even if you did stick him in the rearend. Sometimes things just happen.
a few years back me and my brother shot every day all summer long, opening morning he had a doe come in. while drawing his bow his release came apart and the arrow was sent way over her head. a 1000 shots all summer and it breaks then, so chalk it up to one of those things. good luck findinig him, and or on your next hunt.