Normally, a device will detect the presence of the wireless network by detecting the SSID being broadcast. So if the SSID is not being broadcast, the device will not know the network is there. When connecting to a hidden SSID, the device has to transmit the hidden SSID when searching for the hidden network. So the device probably has to be configured specifically to connect to the hidden network, so that it does the searching differently. With a mobile device, that can mean the device has to keep transmitting the hidden SSID wherever it goes, whenever it searches for wireless networks.