It's complicated, you basic need to store ever item in a hashtable, and then set a number as the first play who picks it up. Every time someone else grabs it, if it doesn't match with the number replace it with the disabled item.
if your not using the hp of an item, you can always use that to keep track
the other simple method is using the custom value of the item
but you basically set one of those two to the player's number, then check the person picking up the item and the oringinal owner of the item, if everything checks out fine, then give the hero that picks up the item the original item, if not then give them the disabled version.
Note that this system creates items, so your gona need to give the created items the same value as the original