Some people just aren't happy unless they are moaning.
Here's a thought - instead of whinging about it being somebody else's responsibility, why not spend probably no more than a couple of minutes picking it up and chucking it in another bag or a wheelie bin if you have one? You've probably spent longer on here moaning about it that it would have taken to do the job.
If it happens every week then you might have a case for reporting the matter - but as a one off, not really. Just get on with it.
A bit of collective responsibility now and again never did anybody any harm, and if everyone did just a tiny bit, then it might even make the street where you live a tidier and happier place.
