have you asked USPS to put a "trace" on it

I ship USPS all the time in my business and very few packages ever lost...those few that were have always been found once I went and filled out the forms for a trace.

even without insurance they still have an obligation. did your husband keep his mailing receipt? that would be essential in finding it or getting at least some reimbursement if it is truly "lost"

hope they find it....