As a seller, I've found it helpful to use the USPS website when packages go missing. Speaking with a postal employee is good. If you've developed a rapport with the Postmaster, that's a great person to ask for help. However, also consider this site:
https://www.usps.com/help/missing-mail.htm
A couple items I've mailed this year got "stuck" at a USPS facility for more than a week. When I used the website, the package got "knocked loose" within a day or two and arrived safely at its destination shortly thereafter.
Something to keep in mind - in my case, it's possible that having a USPS account online helped.
Posting this as a "general help" topic for sellers here. With regard to the OP, the missing satchel makes this case more complex than what I've dealt with.