If it turns out that it's first flight of the day and a similar cowling issue on each side, one is reminded of G-OBMM, February 1995.
http://www.skybrary.aero/bookshelf/books/689.pdf
Edit to add: not in terms of being a boroscope, just in terms of similar work being done on both sides in the same session, and a simple mistake therefore being replicated on both sides.