It wasn't there when the farrier was out 5 weeks ago (he came a week early because our other horse is going to the fair next week), and the vet was out for yearly physicals the last week of July, so it wasn't there then either. Could it be a splint? What exactly is a splint?
It won't let me paste the url so that I can post directly to this page, but here is the link to the pic
hoof.jpg picture by artsyjenn_photos - Photobucket