I know a lot of smaller sellers leave stuff out for pickup.
However, it's a dangerous practice because someone might pick it up on accident or steal it.
This is a risk for leaving something unattended, and really the only one who is responsible is the seller in this case.
Personally, I would never leave something laying around that someone who isn't supposed to have would have access. I also get a receipt for all items passed over, either by individual item, kiosk, scan form etc.
