normally, they will drop a card and tell you where to collect right?
not necessary the nearest pos office, better use the tracking number to track your parcel.

The slip that they leave behind at your mailbox will tell you exactly where your poslaju parcel is. It'll have the address.

Basically the nearest Post Office with Poslaju service, or else nearest Poslaju center.

Call them up and check. When was it posted? If posted on Friday should receive today even if it was posted after cut off time, cause Saturday they were working. If posted Saturday also will arrive today. Unless it was Saturday after cut off time la.