Answer for watched episodes disappear

Nancy and Anonymous, I had that problem too, probably from some accidental set of keystrokes.  They are not actually being deleted. I just resolve it using Nathan and Julius\\\’ solution. The steps are: From a video plugin listing page, press the left arrow to open the menu where you would change the view from List to Thumbnail etc.   Below that under miscellaneous options, deselect the Hide Watched option.  Press the right arrow and you should see the watched/checkmarked videos.