Wi-Fi device detection

In windows, the first page that comes up will have a list of things that are active in the area.

Are they right on the naming reference? LOL

If you see that in the list, there is definitely something there and the hunt is on.

Likely a 5g type connection that is totally bypassing your network. I'd search your place top to bottom for hidden cameras, etc. until you have a clean sheet of devices you can positively identify.

As kiwi mentioned, the battery on these will run down if not maintained. Might be hardwired in somewhere.