I've bought from tundratrader and not had a problem with shipment or communications from him.
Personally I would never have agreed to send a knife like that without insurance. National postal systems all over the world is being infiltrated by crooks and criminals who will steal anything that is not going to cost their employer money (I assume they won't get in trouble if its not tracked) It is so bad that the USPS won't even insure over a certain amount to certain places like the UK. Not that the USPS themselves are that great, I've had my share of problems with them.
Too bad the customs slip doesn't exist any more, the customs number can be used to track a package sent through the USPS on their web site even if its not a trackable service.