just because it isnt conneted to your network dosent mean it isnt sending data over side channels it could:

• use alternative networks provided by other devices (ring cams, amazon echo etc)

• decentral networks like apple or google tracking networks via phones

• it could strait out have a sim card with modem

• sending ultrasonic tones recived by ad tracking networks on smartphones

• high speed IR flickers that could be recived by smartphones distance sensor

• samsung service personal in the building across the street with a big telescope