YES, Android and Apple devices have an application which can DIRECTLY communicate with the Chromecast device even if the TV and Chromecast device are not on your network. Your Chromecast device is in the TV, if the TV is not on the network, then neither TV or Chromecast appear as devices on the network, 'Device Not Found'. Your Windows computer looks for devices on the network to connect to.
I bought the Google Chromecast because my TV while internet capable does not have wireless built-in, I thought I could project/stream/cast my laptop to the TV with Chromecast.