What happens is that someone follows a delivery vehicle, e.g. Australia Post, so they see when delivery is done. If the item is not collected immediately, they wait a few minutes. Then do a quick scan of the area to see if anyone is watching, grab the package and run.
What makes it easier is that with COVID, delivery drivers often no longer get signatures. They like to throw away the package. Then leave as soon as possible without contact with the people at the delivery point. As such, this is a simple endeavour. For whatever reason, a large percentage of these people are women, which is surprising.
This is called parcel theft.
Some common sense is required if you deliver. Let's face it, you are the one who has to prove that the item was delivered.
At the very least, try to avoid leaving items at the door. Put them in a secure spot, not in open view. Then take a photo of the item delivered.
You can then attach the photo to the invoice later in your POS software for your records.