
I can only go by the charity I worked for but frequently donations were left in carrier bags, black bags, the actual donation bags, boxes etc. We only kept a record of how mnay bags the driver bought in, not a record of where they came from, it's just too time consuming.
Actual bone-fide charities are competing with 'rag collectors' who are supposedly collecting for no particular charity rather a collection of several charities, whereas they are actually taking clothes and selling to a rag merchant for their own gain & not a charity.