It happens on occasionally for me, when I'm trying to click activate one thing and somehow steal something else on a table instead. My first accidental steal was trying to talk with Sees-all-colors in the fighter's guild, she stands in front of a table with weapons all laid out, I ran up to her and clicked, stole a 2H mace. My latest accidental steal is they placed a Fire Staff in front of the Woodcrafting Writ delivery chest in Grahtwood, as I went to open the chest to turn in my daily, I ended up clicking the staff and got mangled as a guard past by at the same time.