I can see the little raggamuffin pickpocketing Aidan, but he'll want to catch him and show him some discipline. So it would have to be something worth while, like his grandfather's pocket watch. It might be fun and embarrassing for Aidan to be chasing a lil scamp all around Knockturn Alley or Hogsmeade, but it is his grandfather's pocket watch so there's a lot of monetary and sentimental value to getting it back.