Hidden WiFi networks are not actually hidden in the literal sense. They still broadcast beacons that your wifi chip will see as basically “hidden network beacon lives here”. Your network connect interface just decides not to show you a list with a bunch of useless “(hidden)” entries you can’t do anything with.
Also, when a new client wants to connect to the hidden network, the first thing it does is broadcast an unencrypted message saying “HEY, I’M LOOKING FOR [hidden network name]” so it’s completely trivial to unveil the name of hidden networks given enough time.