Greetings!

Interesting. That serial number seems pre-fire sale. It is low. Perhaps it is registered with empeg. It is not on the registry on the developer BBS. I know you don't want to loose the fingerprints, but it would be worthwhile to see if it is a 60GB unit. In any case:

a) 20GB, he is screwed, sending the wrong product
b) 60GB original, wrong box maybe or just dumb
c) 60GB upgraded with seals broken, he is screwed if he misrepresented it as "under warranty"

Check with your law enforcement contacts for advice. It might be more evidence, especially after they lift any identifying fingerprints, etc. Also, is it in the stolen list?