I am guessing you missed him completely. Did you have him in your sights while almost at full draw? Normally I am in the general area and takes me about a second to get on target after drawing back.
If you know the exact spot of where he was standing when you shot, you could always go back in with a metal detector and sweep the area for your arrow. If you dont have one ask a few friends or even pick up a cheap kids detector from Walmart or something.