As a humble Pax on an Asian carrier into LHR a year or so ago, I was disappointed to discover upon landing that the shoes I had removed from my feet and tucked under the seat in front for the duration of the flight were soaked.
The 'lady' in the seat in front hadn't moved once during the flight, and had left her seat before I realised what she had done. So I missed the opportunity of returning the compliment into her hand luggage.
Flying sure brings the worst out in some folks.