I would go down to the Post Office with the receipt.
Lost. Open a case or call them and give them the tracking # to investigate.
From a Mail carriers experience, I see this as well as get asked this quite often by my customers....considering weather conditions, mail could be and usually is, delayed. However it's always a great idea to have some sort of tracking on everything you send. Might have to pay a little bit more but it's worth it.
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