It's never happened to me with large items.. throughout the years, it's been small items, but as stated above, could have just been missed putting it back in the box.
It should not have been taken due to any fps related issues. If there was some issue like that, they would have held up the whole shipment, and contacted you about it.
As for your "void". Although it's not a nice thought, it's also reality that Customs is really "above the law" and can certianly do what they want, and there's not much you or I could do about it, and they know that. We both know they have there own set of laws and guidelines in their own minds, and I have certainly heard of items going "missing" from others I know (different knives ect..). Hopefully, your supplier just forgot to pack it up for you!
"Fully Retired Retailer" :salute:
Double Edge Airsoft!