I mean, you can't exactly land a big fat Boeing on a strip of bush without any ground tech support... you need a full-featured airport unless you want to risk the machine going up in a huge pile of burning mess upon the landing. Obviously no airport in the region (or planespotters) have noticed the machine landing...
Then, no "oh yeah, we blew up" confessions from terrorists or ransom demands either.
Something smells like fish. Weeks-old rotten fish.
edit: Okay, you can land a Boeing on an improvised landing strip. But preparing a 2km long, 45m wide strip in the middle of nowhere needs lots of manpower to prepare and certainly attracts attention. Unless a nation state sponsored this, no way that this plane was hijacked for passengers/cargo.