It is a reference to the disappearance of South Carolina Governor Mark Sanford who "disappeared" for a week to Argentine on a romantic escapade. His staff and office told the news media that he was "hiking the Appalachian trail."
"The Appalachian Trail" refers to the woman's vagina.
Mark Sanford, the Governor of South Carolina, flew to South America to see his mistress and told everyone, including his staff, that he 'would be gone for a few days hiking the Appalachian Trail.'
Joel Sawyer, Sanford's spokesperson: Uhh...He's... Hiking the Appalachian Trail...Yeah, that's the ticket.