I was battling CC on Showdown, and this just came to me...
What happens if a Choiced Pokemon is locked into a move, and that item is then Knocked Off?
Does the boost/lock stay?
Your Pokémon will no longer be locked in to a move, and the boost disappears, the same way Leftovers doesn't heal you anymore.
and isn't a stat boost like the one you can get from Swords Dance.