Arrows that are shot and in the ground or tree, or where ever .. normally, I think you have a "despawn timer" on them. BUT, if I save my game before your 'despawn timer' runs out .. then the arrows will stay forever.. (pic) .. this picture was taken with the following steps:
Shot some arrows into the ground.
Saved the game.
Exits the game all the way.
Came back into the game and loaded the save.
Played for 30 minutes.
Came back to check my arrows.
Yup. Still there.
#killdespawntimer -- bababooey
Cheers!