Back of a TV is a decent hiding place. Wonder how they found it -was it actively transmitting?
Unless you mean, it happened to be actively transmitting during a(n investigative) sweep.
Still, raises some fun concepts. The sort of things where in this current level of technology you'd almost need to supercool a room for a sweep, blast various RF/sound/etc and look for anything that even remotely warms up, to detect (1) whether something detected something worth recording for later as well as (2) something that might be on the right wavelength/etc to trigger a send.
[0] - https://en.wikipedia.org/wiki/The_Thing_(listening_device)
I was making a joke, but it does look like they got their components from Seeed Studio based on photos.
https://assets.sfstandard.com/image/994911177489/image_k101c...