Whodunit Wellies

Around 10 days ago these wellies appeared in a place I regularly pass on dog walks...in my size, whilst I was contemplating buying new ones...

I know strange things appear in this spot but I'm usually responsible for them or think I know who is.  

I cannot conceive how someone has 'forgotten' they have left them there..and walked off in what?  I can only conclude it is deliberate, but WHY?  I'd love to know.