You cannot find the .cr2 file (never understood why but that is Poser). You appear to be looking for the refrerenced geometry file.

A snippet from MDBridge for Poser, returning the geometry file of the currently setected figure. geomfile should be what you are looking for.

#
#------------------------------------------
# First check if the current actor is a body part or and actual figure
#------------------------------------------
if scene.CurrentActor().IsBodyPart(): 
   fig = scene.CurrentActor().ItsFigure()
elif scene.CurrentActor().IsFigure():
   fig = scene.CurrentFigure()
else:
   fig = None

if not fig is None: 
   geomfile = fig.GeomFileName()
   gf = os.path.basename(geomfile)