What a thoughtful question.
I was really worried about the cases getting lost in transit. That's why I insisted on only sending them out via a method that had some form of tracking. For within the US, the cases will be sent using US Post Office Priority Mail with delivery confirmation. For Canada and International shipments they'll be sent via registered mail. This means that the post office will internally track the package until it reaches you.
Also note that registered mail takes longer to reach its destination than regular mail (due to the special handling), but the added security is worth it in the long run.