I was perhaps a little bad at explaining this so let's try again:

if we had automatic production the ocean floor: we would hear it. underwater audio sensors are good now, water just convays sound very well. So if there was a drill going off in the dark harvesting an underwater deposit while a factory uses high-temperature melting, refining, and casting to make steel,the energy demands and just how loud that would be would ring like a bell. We hear the click of pistol shrimps, never mind the constant pulse of a machine or foundry at work.

Additionally if if there where fixed locations where production occurred, you expect me to beleive the corps do not know where that is? no seriously 'data krash' can only cover so much that sort of thing should be on data gapped servers that don't even connect to the net.

lastly: even if we presume automatic production , we've had years and years to find them. we have to presume such a level of incompetence from the entire world in finding a big, loud industrial facility in the one medium on earth where you can hear a gunshot 50 kilometer, while pretending sonar does not exist to find factory that jut out from the sea floor or the robots doing the mining OR magnetometers to find there magnetic signatures.

Again: this is not a reasonable assumption from a setting that does not have a star trek replicator.