Destroy the speaker and hide the device inside a tire, steerer tube, or other such place?
I mean the thief will get notified, but what are they going to do? Dismount tires, disassemble steering assembly, remove the grips, undo the saddle, bottle mount, Garmin mount, bash guard, lights, etc? This all takes time and skill, it can’t be done on the spot and if they dragged the bike home or to a fence they have already disclosed the location.