That was 1000NM West of PER, not 1000km. A rather substantial difference.
If the aircraft went South, it would be because there was extra fuel uploaded to make Africa.
There's only two airstrips in the Northern Indian Ocean (besides DG) - CCK (8000') and XCH (6900').
Both of these are well-established Australian territories with top-class communications, and I'm sure we'd have heard by now if a stray B777 rolled up to either. Unless it was a weekend, of course.
