I also question why, if his vacation was innocent, he instructed his staff to lie and say he was "hiking the Appalachian trail."
I wouldn't say that the fact his staff said he was hiking on the Appalachian trail is any evidence of a cover-up. In fact, I'd say the timing of the announcement seems to indicate that it wasn't a cover-up; if he had instructed his staff to say so, they would've told people as soon as it was clear this was a political story, and people would've in general shrugged their shoulders and said "oh, that crazy Sanford!" and went about their business. Rather, I think some staffer recalled Sanford saying something about wanting to hike the Appalachian Trail (as he said he was considering doing before he decided last minute to go to Buenos Aires
), told his superiors, and they decided that the info was credible enough that that was the story they were going to roll with.