Does the "Powerful Cantrip" feat works?

This just happened to me. My wizard with "Powerful Cantrip" shot the "Fire bolt" to the enemy, and it misses. But the enemy takes zero damage. 

Explanation on "powerful cantrip" says: 

"When a creature succeeds on a saving throw against your cantrip or dodges your cantrip, the creature takes half damage but suffers no additional effect from the cantrip."

I think the missed firebolt should've caused a half amount of damage... Or am I understand this in a wrong way?