Just a thought, but you might try and find out the routes the airplane your friend was on followed that day. Aircraft are spruced up between flights at various stations, but serious cleaning only occurs at the end of the day. If you can find out where the Acft overnighted, you can work backwards from there.

Maybe an appeal to some of the more connected FT'ers can give you a tail number and a route. hints to Empress, Parnel and Shareholder et alles

DF