[leoedin]

If you're looking for a ship you're going to have much more success with a synthetic aperture radar satellite. They work through clouds and at night, and the bright reflection of a ship's flat steel plates is fairly easy to spot against the background clutter of the sea.

Unfortunately they generally cost hundreds of millions of dollars and there's only a handful of them in operation.

If a western government actually wanted to look for this ship (while it was still floating, anyway), they'd almost certainly find it. There's whole divisions of the air force and navy trained to do exactly that. The cost of the search would be pretty much unjustifiable though.