Worked for UPS in International Shipment Resolution for 15 years. Missing merch is known as "fall out." UPS would have been responsible for ensuring receiver got a replacement. USPS sends you the mangled shipping envelope with the explanation that USPS sorting equipment is responsible for the destroyed or missing publication and not so much as even "have a nice day." They admit responsibility for the loss/damage and it's up to the receiver to contact the shipper and request replacement. If this government run-around sounds familiar you've likely already experienced it. Just saying.
I received Hop Up #3 the other day. No packing envelope at all. Just the shrink wrapped magazine. Luckily, the magazine was in great condition with no damage. Hop Up #2 shipped in a mailer envelope and arrived here just fine. Seems like they're still sorting out shipping options.