Pack Rat

Pack Rats are real rodents that live in the desert. In their foraging, should they chance upon a shiny treasure, they will drop what they are carrying and take their new treasure home. Their burrows are filled with all of the little treasures that they have found.
So, a slumbering camper might find in the morning that the spot where they left their watch has been replaced by a stick. Or, someone might find that at home, all of their favorite pens that make writing a joy, have slowly been replaced by cheap-o pharmaceutical pens that hardly write at all, and someone else's backpack is full of someone's favorite pens... for example.