The hide is not at the posted coordinates, but it is another library cache, of course.
Harry managed to cram a lot of adventure into a couple of years of school. Consider just these few examples.
- Goodbye
- the Dungeon
- Field Day Revenge
- Drop of Doom
- Green Slime
- Halloween
- the Code
- Ropes minus Mud Gremlins
- Christmas Surprise
- Battle of the Bugs
You can validate your puzzle solution with certitude.