Missing Something?

Friday morning, Tania ran in to the kitchen, and asked anxiously, "Mommy, where go my bum?"
"What," came the confused reply.
"I say, where my bum? I can't find it."
A few moments of silence, then, "Tania, it's your bum. It's where it always is."
Tania turned to see if her mother was correct, and spun around a few times like a puppy chasing her tail. She then looked up and said with a giggle, "Silly bum. It hiding."