Thanks for the replies.
I can't get a screenshot as when I open gtk-screenshot it becomes the latest window opened and the previous ghost disappears!
To replicate this (if you want to!)...
Fresh install 7.0 lite
Switch to desktop 2 open leafpad then close it - the window outline remains visible in the pager.
Switch back to desktop 1 and the outline disappears.
Like I said, not a huge problem just a niggle!