That's a fair point, but it doesn't seem extremely likely. I could see developing "fog" on/in the device (like glasses fogging when coming in from the cold), but enough to produce a short is hard to believe. The aluminum should actually reach equilibrium with the environment faster than plastic.
I can think of a pretty easy hypothetical--have the laptop indoors, powered down in a very cool air conditioned room for enough time to make it cool. Then take it outside in a high humidity region like Florida and turn it on. Bam, condensation inside the device.