1. You can track LS985572828CN, on this site:
http://www.track-chinapost.com/track.php?code=LS985572828CN&fc=0
Or this site:
http://tools.usps.com/go/TrackConfirmAction.action?tRef=fullpage&tLc=1&text28777=&tLabels=LS985572828CN

2. Both site are saying the same thing:
2016-06-30 16:42
EVERETT, MA 02149, Delivered, In/At Mailbox, Your item was delivered in or at the mailbox at 4:42 pm on June 30, 2016 in EVERETT, MA 02149.

3. The parcel was delivered In/At Mailbox, the only thing that come into my mind is that the parcel was not put in the right mail box, other then that I don't see anything. Or the parcel was put in the mail box but eventually was stolen because the mail box was not secure enough.

4. Recipient could call USPS to find out if by any chances the parcel was put in the wrong mail box. Depending of the answer, seller can have China Post launch an investigation about the parcel.

5. Because this is E Packet, this type of parcel are fast to be delivered but the draw back is that it's not registered mail, so nobody have to sign for the parcel.

Hope this help.