Pokemon Best Wishes! - episode 28 - 20 Apr, 2011

On the road to Nimbasa City, Ash and Co. come across a trainer named Stephan who challenges Ash to a battle. Stephan sends out his Blitzle while Ash sends out Oshawott, who blocks Blitzle's attack with his Scalchop shell, only to lose it mid-battle. Oshawott runs off to try to find it, ending the battle prematurely. (Source: Wikipedia)