I got a weird circumstance, the highlighter box is "tied" to a linear takeoff. When I hide / unhide the takeoff, it hides / unhides the highlight.
Very strange. We will dig into this. If you have any extra details for what project and page this is on, please let us now here (or you can send it to our live support chat if you prefer to keep it more private). We will check to see if we can find what's happening on it.