User blog comment:SayuriDarling/The Mark of Athena Official Discussion/@comment-71.60.55.121-20121009101722/@comment-3146930-20121009103714

Well Percy called his mom when he was in Alaska, leaving her a message. Since The Mark of Athena takes place right after The Son of Neptune, she at least knows that he isn't missing anymore...except now he is in Tartarus and the only people that know how to contact her (Percy and Annabeth) are out of cell phone range. I'm sure Chiron knows how to get a hold of her, so he could tell her what is happening.