anyone who buys by mail order should insist on having the package fully insured up the the amount to cover the goods inside,it does cost a few more quid but can stop a lot of bad blood.
A parcel which has bee sent can then be tracked aslo paying the extra is proof of postage.I have been sending parts through mail order for over 15 years and yes I have had parcels damged,lost and turn up late but at all times my custumer and I have known that there money and my good are covered.
If a item is sent a fair time to start worring is about 7 days after postage,but as I said if sent correctly a tracking number is available to proove its been sent
There obviously something wrong if the sender is not replying to your PMs,I would be chasing the problem up