It looks like its part of the Minifigures in those sets
Thanks - I hadn't realised that could be the case.
When you go into the inventory for a set, there is another drop down where you
can adjust the "view". Here if you select "Break Minifigure", it will add all
the minifig parts to the inventory list as well. Good thing to remember when
you run into sets with brick built minifigs and such.