How does a Boeing jet simply "lose contact" with air traffic control without prior knowledge of its coordinates etc?

Shouldn’t it be fairly easy to locate a giant hunk of metal in the sky that was “set on a course and route” anyways?

Ok I don’t meant to come off as assumptious as I am. I’m genuinely curious and no means meant to be judgmental. I hope everyone on board the Malaysian airplane is safe and just lost contact due to electrical problems with contact only.

Here’s a story so you can catch up