A few years back I worked in a big old building with open plan office areas and very lax (ie asleep most of the time) security. We noticed things going missing from desks and from jacket pockets when hung up. I lost my 21st birthday present gold pen in this way so was very p'd off.
One day, a colleague spotted a guy rifling jackets in another team's office area and chased him with another colleague. When they caught him, they weren't gentle in getting back the wallets and other stuff he had on him. However, none of us expected the police to arrest him and colleague at the same time as the thief ! Fortunately his dad was a solicitor and the police eventually backed down on trying to caution him.