FF6 - Brave New World

You could make an open chest sprite graphic, put it in some empty space and direct an overworld sprite pointer there, then update the entrance event to check the event bit you use to obtain the item to decide if it should apply the "open chest" sprite.

Edit: or better yet, expand the existing chest graphic so all you have to do is change the "pose" of the chest, that way you wouldn't have to find a random "blank" pointer, you can just keep the same one the chest already uses.

Edit 2: You could also keep the blank chest graphic up all the time and put the chest NPC on top of it, and have the entrance event hide the object if the item has been taken from the chest...