You hold your knife between your teeth, keeping it accessible while your hands are busy picking a noble's unguarded luggage. Leaving anything valuable without a guard is like an invitation to steal it...at least that's been your experience.
With a satisfying click! the lock comes undone and you pry the chest open to reveal--oh, yes! That will do nicely. You pocket what looks to be a sizeable purse of Copper Eagles and a few interesting looking weapons, before carefully replacing the lock and sneaking out of the tent undetected.