Debug Pie never goes off the screen when shown. This ONLY applies to the Pie, the FPS+TPS counter works fine.
How to recreate:
1. Press F3+Shift
If it doesn't work, check if you are on 20w06a.
It stayes on the Title Screen and Singleplayer Screen, as well as Multiplayer. Relaunching the game is the only way to get it off.
Gamemode: Tested in Creative and Spectator