Of course no one will admit to ever leaving their coolant recovery tank cap
on the back bumper and driving away with out installing it and having it
roll down the road somewhere, so here's what  I did to fix it short term til
VW order's me another.  Went to flaps and bought a 1 3/4" rubber expanding
freeze plug and shoved it in and tightened the nut ever so slightly.  Will
report on how hard it is to get out when the time comes.  The minicell foam
plug I whittled fit okay, but wasn't sure it would tolerate the heat.  Come
to think of it, that old sock might've worked too.  No wait a minute,
PLAY-DOH!!

DM&FS