Go to a webpage and use the menu item to block a picture.
Result: the picture is gone, but so is the menu item 'Block Element'.
You have to go to another webpage and return, to get the menu item back.
Blocking a picture with Block Element from the Adblock pull down menu has the same effect: the menu item in the browser disappears.
Windows 10 Home.
Chrome version 69.0.3497.81 (Official build) (64-bits).