Ok let's say:
Garchomp mega-evolved into Mega Garchomp!
The opposing Ambipom used Fling!
It flung it's Life Orb at Garchomp!
Garchomp used Dragon Claw!
Garchomp lost some of it's HP!
But we all know the Mega Stone of a Pokemon cannot be replaced in battle. So will Garchomp have a Life Orb or its original item (Garchompite)?
I'm asking because my item got replaced earlier today at the Battle Maison again.
Fling doesn't forcibly replace the opponent's item with the one flung. It just does damage and has a possible secondary effect based on the item thrown. With life orb, it inflicts 30 base damage to the opponent.
To give your opponent an item, you would need a move like trick or switcheroo to switch items, and even then, mega stones are an exception in that they cannot be removed from the Pokemon when in use.