Why didn't McCain cite"cross story" until 1999? 25 years AFTER his captivity

Andrew Sullivan notes (via Jed) that it's a bit odd that McCain's story about the prison guard drawing a cross in the sand doesn't appear in McCain's detailed account of his captivity, circa 1973. The first time that I've been able to find McCain mentioning this story is 1999, a full quarter of a century after he was released. If it was such a pivotal story in his life, why did we not hear about it until McCain had decided to run for president? And before we get the typical bluster from the McCain camp, and the Republicans, and the media, please just stop it. Andrew is a conservative and a devout Christian, if he is asking this question, I dare anyone to claim that it's partisan or sacrilegious or whatever. Unless the new standard of journalism is that politicians don't ever lie - or even that former POWs don't lie - then we have the right, and the media has the duty, to ask the question.