Sorry, but either the Postal Service either 
hasn't really been that willing to help and/or 
they really couldn't find out anything.

The postal inspector I ended up talking to 
(months later) told me that he couldn't find out 
anything and (get this) was hoping for a SECOND 
incident to occur in order to sniff out a trail 
and track down a suspect.  But since the cels 
never re-appeared, he's guessing that the person 
(postal worker or not) probably stole the 
package, looked inside, had no idea what it was, 
and tossed it in the garbage to cover his/her 
tracks.

In terms of insurance, that was handled by the 
Japan Post Office.  The best they would (notice 
that I didn't say 'could') do was reimburse the 
shipper (the dealer) the amount the package was 
insured for MINUS the shipping cost and in yen.  
But at that time, the exchange rate was probably 
the worst it could have been in the past 3 
years, so I got screwed out of more money 
anyway.  So maybe it was only 80% of my original 
payment that ultimately got recovered?  Not to 
mention the value of the lost cels FAR 
outweighed my original payment anyway...

But after fighting tooth and nail for this so 
long, there basically has been nothing else I 
could do except bite the bullet.