Sandy Burger was in the National Archives looking for 9/11 information to give his testimony to the commission. He stole documents when he found them. I doubt he'd leave damning info like the Able Danger documents alone. My guess is they went out in Burgers pants.
It is odd, isn't it, that the documents that HE stole are from the same time frame that the Able Danger "missing" documents are from, huh?