It is possible you have noticed in your travels these apparently mischevious cherubs wandering about the land, periodically stealing items you may have found lying around as you explore. Often these cherubs and their thefts can be cause for much frustration and it is true their exuberence sometimes gets the better of these naturally impatient beasts. However, the cherubs are not genuine thieves. They serve a purpose in the land - the smooth running, and safe restoration/circulation of items designated part of quests, puzzles or those forbidden from long term ownership by any one mortal. Thus the cherubs regularly chase down each item in the land carrying this flag and, when they happen to notice it not in its rightful place (ready for the completion of the quest, puzzle or purpose it was intended) they dart in, quick-as-a-flash, and pickpocket the item away.
You should not despair. The cherubs tend to place the special items in predetermined locations about the land. Learn these locations and you can plot your own routes for completing profitable, experience-garnering questing sessions.
If you are unsure whether an item you have found is part of the cherubic grand design examine it and if anywhere you see the words 'it belongs to you' you will know immediately the item will never come under the jurisdication of these ever-vigilant little darlings. Items purchased in shops or fashioned by cities, guilds or individuals with appropriate skills are never vulnerable to cherub theft... so if you seek to build an inventory of great potency, these are the routes to take to do so. Good luck.