This is pathetic customer service from all involved. Everyone is passing the buck and trying to save their ass; and in the end the customer gets screwed over.
Who in their sane minds would have known that a package is pilfered and hence needs to be opened in front of witnesses; and that too, at the post office ?? :1ign22:
In a way, you are lucky because this was a cheap item (relatively speaking). I shudder to think about what it would be like if this happens with something expensive.
I guess the only 'safe' option is to use reliable couriers like UPS or FedEx.