Somebody emptied my wheelie bins

Some time on Friday/Saturday my 2 recycling wheelie bins disappeared from my back yard. I found them on the back street and they were fully empty. I presumed that the collection day had changed and maybe a neighbour took them out for me. Except it's collection day tomorrow and every neighbour has their bins out and they're all full.

What's happened? Anybody got a clue? If it was just one bin I could guess that somebody needed cardboard or aluminium or was trying to steal my identity. I'd be fine with that. But who would take both?!?