Charity shop volunteer here:
It might have been the rubbish from the charity shop which most have to leave outside as they use private recycling companies.
Sometimes (whisper it) shops leave stuff for people to nick as it's cheaper than paying for council to remove it.
If it was a donation, hey, anything decent always gets stolen by morning anyway. In London professional scavengers do the bins as a matter of course.
Having said all that, I once picked up a sack of donations outside my shop about 9pm one night when I was coming back from somewhere else and hopped on the bus with it to bring in for when I next came to work.
A purple-faced 'lady' in her 60s approached me as the bus took off. She was shuddering with rage and hissed 'Stealing....from a charity... how could you... stealing from the sick'. Spit went all over me.
I smiled and said sweetly 'I work for the sick. For nothing. Like you do, I am sure, Madam'.
Beetroot Face sat down, everyone moving up hastily in case spit went on them too. There was a tiny bit of applause 
Never seen her again, but Beetroot Face is a MNetter for sure.