[Gameplay] Bone Plating not working?

I picked Bone Plating on Yasuo last game, and in the post-game stats it said that it blocked 0 damage. According to how the rune is worded, if you take damage from a champion, for the next 5 seconds the next 3 hits you take should do reduced damage. I was laning against Fiora and ulted into the middle of the enemy team a few times, so there is no way I didn't take any hits within 5 seconds of taking damage for the entire game. Is this a bug, or am I just misunderstanding how the rune works?

edit Apparently I'm not the only one that experienced this, here's a much better post by Lil Homie busta explaining the exact same thing