The Forgotten Helper — Lorrie Moore

Aben is Santa's best toy maker. He is also Santa's grouchiest, most ill-behaved elf. On Christmas Eve while Santa and the other elves are delivering gifts, Aben's task is to watch the reindeer. But at the very last house, Aben sneaks down the chimney to take a look around. When he comes back up to the roof, Santa, the elves, and the sleigh are gone! Aben must wait a whole year until Santa returns. As the stranded Aben investigates the house, he finds a young girl who is as grouchy and mischievous as he is. No wonder Santa almost didn't stop to bring Ivy gifts this year. And who's to say he will next year if this incorrigible girl doesn't learn to behave? So begins Aben's adventure: he must learn about Ivy and devise a plan to ensure that Santa will come back for him next Christmas Eve.