Opportunistic
Never has the phrase “you snooze, you lose” been more relevant than in the situation pictured here. We don’t know how long the owner of the car and pizza had been gone from their vehicle, perhaps it had only been a few minutes, but they left their window open. They probably thought it was just helping air circulate.
They probably didn’t think that this open window would be seen as an invitation for some passer-by to nab a slice of their pizza. Who is hungry, and cheeky, enough to wander past a car, see a whole pizza and think that it would be ok to grab a slice?