Add two potions, one to lock and one to unlock items. By pouring the lock potion on an item that is on the ground it removes the option to pick it up. Pouring the unlock potion restores the ability to pick it up. The item can still be interacted with in any other way that is allowable when it is on the ground - e.g. a note can be read, a piggy feeder can be filled.
Ideally the value of lock potions should be around 200 to 300 currants a use and unlock potions should be more expensive, around 400-500 currants per use.
Why? This would allow people to leave items in their streets without fear of them being taken because it would cost more to take a feeder, or a meat or milk collector than the item is worth to the person taking it. It would also allow people to leave notes in places that could last a little longer. It could also be used for decorative purposes both on home streets and in public places.