Who spits on a saddle?

Earlier today I returned to my bike, to find about a dessert-spoonful of saliva on my saddle. While I'm aware that this could be accidental, I'm led to believe it was a deliberate act, particularly given the location of saliva right in the middle groove of the saddle. Additionally, the Sheffield stand was situated under a roof and it was unlikely that someone spat and it unintentionally landed on my saddle.

Anyway, my bike was locked off Torrington place, next to a lime green SS with white Halo Aerorage wheels and Crank Bros eggbeater. If you're on here did you also have saliva on your saddle or did you possibly spit on my saddle?

I'm aware there's nothing I can do, and there's no need to get in 'a malaise' about it, it just seems inexplicably dickish.

This is London, my friend.