Assuming that all these headsets are bluetooth "classic", since I am yet to see a bluetooth low energy headset, how could they be tracked, anyway? Were the hea

Assuming that all these headsets are bluetooth "classic", since I am yet to see a bluetooth low energy headset, how could they be tracked, anyway? Were the headsets all in "discoverable" mode ? Are headsets announcing their MACs even when not in discoverable mode ? Or do they broadcast their MACs in plain text even during a paired&encrypted connection ?