Why doesn't Poseidon help Percy (Jackson) in the 6th book?

To hell with all this 'The gods dont interfere' business...Hera took Percy and Jason and swooped them. So why doesn't Poseidon be the father he is to Percy and go get his son back from Lupa. He knows what is going to happen to his son but yet he sits around and does nothing! I am losing faith in Poseidon, he is NOT the god I thought he was. He makes out in book 1-5 that he is the loving dad who wants the best for his son but then Hera comes along and takes his son away and he doesn't even raise an eyebrow. The jerk! I though Hermes was bad was leaving Luke but at least Hermes tried to help Luke. Poseidon is just going to leave Percy at the roman camp to rot