My desk and bottle tops....

Ok, the first few times I though that someone had left a bottle top by my desk my mistake... then it happened again and now this morning I find bottle top number 3... Judging by the colour its a Dr Pepper drinker on this occasion... (I don't recall the previous colours...)
So it seems that not only does my office have a phamtom pooer, and boggie man but also now a phanton bottletopper....
This time I'm going to leave the top where it is to see if...
a) The cleaners actually do their job
b) To see if this dumping activity continues....