Poseidon had recently claimed his child whom currently resides at Camp half blood, where she's learning how to control her abilities and learn all about the mythical world. He hadn't had time to see her, all be could do was claim her.

Considering she's a forbidden child, meaning her being conceived meant that Poseidon had broken the pact that he and his other brothers had made to agree that they would have no more children...since she is a forbidden child, it means she's in even more danger.

Most of the Gods don't actually bother to speak, contact or visit their children, after all many of them have far too many children to be able to do that and overall the Gods aren't the best parents. Camp Half Blood exists within a separate area of the world, separated by a mist that only Demigods, Satyrs and magical creatures can pass through, but most importantly, no monsters can get through. Meaning Poseidon's daughter would be safe there.

Finally, after a long time of being in the shadows, watching his daughter from afar, Poseidon transports down to Camp Half Blood.