The first problem appeared when the woman attending the office said: "If you don't receive the parcel in 2 months, go to your postal service with this receipt to claim it". False, of course. My local postal service can only track the shipment if they already got it.
Second step (and second problem), try to track the parcel through http://ems.posindonesia.co.id/. Some options don't work, some aren't translated to English and the tracking didn't work until I sent several email messages to Pos Indonesia.
When it finally worked the parcel was already lost but the information was so cryptic that I didn't notice it:
Departure from inward OE to 80000 Adpis : 000192What does it mean? After browsing their website several times I realized that "OE" means "office of exchange", 80000 is the code for Bali main office, "Adpis" is the indonesian word for "Advice" and 000192 seems to mean (there's no translation) that there was a problem with the parcel and I need to pay more to get it.
OK, I'll send them a new email to ask about it...