lost item

I think that's by the gate for the confiscated items outside. When you're outside the main door from hogwarts turn right, you'll come to the quad with the one little tree in the middle. Follow that to where you took your flying lessons, and to the left there'll be 3 star trees and an entrance to a rickety bridge and the confiscated items door. Get on your broom there, fly over the rickety bridge to the left and there'll be a square patch of grass kind of behind the entrance to the rickety bridge to the left, it's on there on the patch of grass.