Throwing any looted items near the entrance of any instance, is the fastest method to despawn items. When people ask, "What is the quickest way to get rid of junk you do not want if unable to use the Obliterator? I always tell them, "Throw it down near the entrance of an instance, Burial Chamber, Troll Cave, Sunken Crypt or Frost Cave. It will disappear after a day cycle, or log off."

Why would you think that leaving items on the ground is a viable method to secure them for future use? Why would you not leave them on your character, or secure them inside a chest. You can even leave items in the chests inside instances, they will remain there until removed by a player.