matblack i think youve found the crew on that flight
inkjet with frost you get an more even spread over the wing. Cold soak does not affect the metal, meaning the spar and stringers across the chord. Looks like cold soak to me.
Just because things don't go wrong doesn't mean that everything was alright. Snobby passengers who know it all are not appreciated but a genuine question relating to a safety concern is always welcome. Any 'professional' not being able to deal with that is your true amateur.