I'm assuming the ship would be fortified to such a degree that by the time you could "hack" into the steering system or offload any decent amount of cargo, the authorities would have been notified and would be en route.

Not to mention the fact that pirates seem to want to steal the whole ship and appear to be ill-equipped to offload cargo.

Ships already disappear regularly on the high seas.

Some especially attentive news watchers may be aware that a large commercial airliner is though to have been lost without a trace in the recent past.

http://www.cnn.com/2013/02/08/world/asia/asia-piracy/index.h...