How do you think they catch grow-houses? They thermal scan neighborhoods for heat signatures from the grow lights. Cops are masters of subverting the law to do whatever they want.

I know thermal imaging has been used to look for marijuana farms, back when grow lamps were incandescent and houses would stand out as hot. But I don't know if they had warrants for those or not.

But to actually use imaging, whether it's thermal, radio, or X-ray, to see through a wall, is definitely considered a search.

Thermal cameras can't see through glass, but they could be used to see if a building is significantly warmer than the surrounding structures.