As luck would have it, I discovered the wonky shoe while chatting with the ranch owner. As I gave it the stink eye and tapped it ineffectively with my hoof pick, she told me to hang on a second as she had a good pair of nippers that I could borrow.
With all of Izzy's new space, he's able to do a lot more zooming around. I am also hosing him off more frequently which has softened up his feet. Woo-hooing with soft feet is a good way to irritate your farrier. Izzy was due for shoes this week anyway, so I guess the timing was good.