USA, Canada / Packages sent from Poland to USA "held" in customs? [13]

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The parcel sent from the US to Poland, stuck at "WER Warszawa, Customs clearance"?

Hello. HELP!!!

Did not receive the parcel, and sending back to the sender did not return.
At the post office US from where it were sent they said that it should be at the post office Poland...
tools.usps.com/go/TrackConfirmAction?tLabels=lh011390718us
And at the post office US said that this line "March 8, 2017, 5:15 pm Departed CHICAGO, UNITED STATES" --- error line in tracking...

How long can keep the parcel at the Customs Clearance?
What to do and where to go to search for the parcel?

Can someone tell me the address, and the phone to clarify where the package is...