Mebbe that is why they turned around?
I think you are onto something. What sort of airliner operates safely with a pressurized, heated cabin that communicates spacially with a non-pressurized, unheated cargo hold? (If that is indeed the case.)
Will the moron who inserted his/her laptop into some oddball crack in the fuselage get to pay for the fuel, crew, and the time/ruined trips of all the other passengers? I hope so.