Chests create ghosts as soon as the player is far enough (out of render distance of the blocks). This "ghost" is only visually there; you can pass through it, it can exist through other block and entities. Once the "ghost" exist, you can do anything to the chest and the ghost will still exist. Ghost chest don't disappear with time, but they do disappear if you "save and quit to title".
Place where you can see them:
Inside a chest that you open. (Looks like the chest has two lid.)
Where a chest was after destroying a chest.
Where a small chest was before it was transformed into a large chest.
– In multiplayer, ghost chests may exist only in the world of a single player. Only the players who leaved the area after seeing the chest will have a ghost chest.
Steps to reproduce:
1- Place two chests then go away, far enough for the place where the chests are to disappear (out of render distance)
2- Then come back and breaks one chest and makes a double chest with the other one
3- You now have a ghost small chest and the ghost of a small chest inside a chest