What cabin should Percy Jackson really be in?

In Rick Riordan's Percy Jackson and the Olympians: The Lightning Thief, all of the kids at Camp Half-Blood are assigned to a cabin based on which Greek god is their parent. For example, Annabeth lives in cabin 6, for the children of the goddess Athena, and Clarisse lives in cabin 5, for the children of the god Ares.
When Percy first arrives at Camp Half-Blood, nobody knows which god Percy is the son of yet. For the time being, he is taken in to cabin 11, where the children of Hermes stay. Hermes is the god of travelers (among other things), and so Percy is welcome there.
Eventually, it is discovered that Percy's father is Poseidon, the god of the sea. At the beginning of Chapter 9, he has been moved to Poseidon's cabin, which is cabin 3. Percy feels isolated and "absolutely miserable" in this cabin, as he is the only person living there. Poseidon doesn't have any other known demigod children, because he made a promise not to have any children with humans and broke that promise by having a child with Percy's mother Sally, a human woman.