Ants are badass, ridiculously strong, and he probably just wiggled his way under/through whatever low pressure gasket/seal is in place for dust. This device is not air tight by any definition. He just wanted to get to the sweet candy jelly beans inside.
Ant penetration resistance should be added to every device spec and properly tested.
Youtube: "Xperia Z Official Ant Testing". "The Xperia Z is water resistant up to 1 meter for 30 minutes, and ant resistant up to 150 ants for 45 minutes. Results may vary with ant species and water purity."