They do and can flyover and see your heat sig before getting a warrant.
If they suspect you're growing by seeing your heat sig....they I.D. the address. Then look into records of the person who lives there. CC transactions, shipments from delivery companies (ups, fed ex), your arrest background etc. Is al looked into.
If they see something else....like a bunch of charges to seed banks or you've been arrested for dealing or frequent deliveries from hydroshops.....they may pay you a visit.
But all would be a result of the flyover when they saw your heat sig. Its not that hard to dig into your info.
My question is....is there any material you use to line your growroom with that can block their FLIR?
I guess this is a plus in the CFL users side. I would think that HID lights are a lot easier to identify using FLIR.