I certainly hope we can be pickpocketed (occasionally).
Without stats for the NPC (Dexterity, Agility), the player (Intelligence, Perception, Wisdom), or a Pickpocket skill, how do you think the game would determine NPC's chance of success and your chance to detect the attempt?
Obviously, the simplest method is a check vs. your character's sneak. I'm pretty sure, never done it myself of course, that someone used to picking pockets, and moving quietly, would have a better idea than anyone else that they have been 'marked' themselves.
@Sage. When is a child too young to play a game? When they are young enough to be influenced by it.