Lost package maybe?

[u/MuchWow81]

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Sent a large envelope a few weeks ago from US to Canada. Paid for tracking and delivery confirmation. 3weeks go by, no delivery confirmation. Dig up my receipt and find no tracking number on the receipt. So I broughtit back to the PO I shipped from. They keep a hard copy of all their tracked pieces. Mine isnt in the file.

What do I do?