Kili would have preferred a job of more importance, but if Thorin wanted the ponies to be watched, then that is what he would do. Or, that is what he [i]should[/i] have been doing. The task was so mundane that he did not treat it with much seriousness. They were in the woods, after all. The ponies could not get far, and they would be sure to make noise if a threat were to approach.

As a result of such carelessness, it wasn't long until he realized that two of the ponies were nowhere to be found. The youngest exchanged alarmed glances with Fili, and he signaled for him to keep quiet. He didn't want to risk telling Saeril. Carefully, he and Fili approached a fallen log, and both brothers stared out into the darkened forest. Somehow it seemed ten times as intimidating right now.
Before Kili could decide their next course of action, he overheard footsteps easily identifiable as Bilbo's.

"Here you are." Bilbo had managed to carry three, and he passed one to Saeril before he took notice of both brothers being more quiet than usual. "What's the matter?" 
Kili didn't look away, his eyes remained on the trees ahead. "We were supposed to be watching the ponies." He glanced to Fili nervously, as he was also to confirm the fact. "We had sixteen. Daisy and Bungo are missing."
Bilbo blinked in surprise, bowls still in hand. "Well, that’s not good. That is not good at all. Shouldn’t we tell Thorin?"