semidemiurge <rick.fetters@gmail.com> found these unused words:

Let your family Lawyer talk to them ???

The advantage you have is that the plug is a relatively large diameter
object so you have some room to play with.  Assuming the plug hole is
accessable, get all of the center electrode out so that there is just
a hole left in the center of what used to be a spark plug.  Yes, there
will likely be some pieces that get into the cylinder.  Get that
piston at top dead center on a compression stroke before you start to
help minimize the volume in which the pieces can travel.  You'll just
have to risk it.  Once there is a hole, insert an appropriate easy-out
and try to back out the threads of the former plug.  Use lots of
penetrant.  You might luck out and be able to remove it.  If you get
it out, work a flexible magnet through the spark plug hole and into
the combustion chamber to try to pick up as many metallic pieces that
may have fallen in as is possible.  I'd also rig up a vacuum pump,
such as a Mighty-Vac, to try to suck up non-ferrous pieces.  The moral
of this story is that one NEVER, NEVER inserts a spark plug (or any
other bolt on a machine for that matter) without a liberal coating of
anti-seize compund on the threads.  Good luck.  Al