Dont worry. It will turn up. Usually, USPS doesnt update that often, atleast here in US. I have received items, with no details of the item available in the system from amazon( not normal mail but the ones with tracking).
Also, my sister posted three parcels(books) from UK, one turned up the next week. The second one after three weeks and the third after four weeks.
Post works just like CIC. Out of three applies at the same time, one receives ppr fast and the rest God knows when..
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I am sure you will get it today.