Sending a message about stealing? John Reese intimidation.
Not only would you get a full confession from your evil yogurt-stealing coworker, but you'd also get a year's supply free of charge thanks to John Reese.
Reese would definitely know the right things to say to make sure a snack burglar changes his ways. Furthermore, you'd never be left hungry at the fridge for at least one year, as a conversation with Reese would give the thief added incentive to make up for his crimes by purchasing your future yogurt him/herself.
Watch Person Of Interest Tuesdays at 10/9c.