On a warship? They’d have still seen it.
It took 6 months to discover, and even then it was by techs who went to physically install different hardware saw the dish hardware mounted to the ship. That's the real WTF here, how do these ships not have some kind of passive RF scanning/rogue AP detection??
It was seen by regular enlisted people who saw the network on their phones and left comment sheets asking WTF it was, but the person in question snatched up the papers before they got to the officers. If they had hidden the SSID, nobody would have seen it because nobody scans for hidden SSIDs on their phones.
iPhones don't come with those expensive high-bandwidth cables, they come with charging cables that only do USB 2.0