As far as I am aware, and maybe a criminal defense lawyer like
@Mr Person can back me up, but criminal case files from the DOJ are not the same sort of thing as diplomatic papers that have multiple copies (albeit under top secret seal) for multiple different sets of eyes, like the President, ambassadors, state department officials etc.
Criminal evidence is usually kept in a secure location. It is not something a staff member of the White House could just walk in and rifle around with, or even just any DoJ employee. Especially evidence involving children engaging in sex acts recorded in photographs and videos and the like, where the mere act of knowingly possessing it is a criminal offense? I welcome people correcting me if I am wrong, but those pieces of evidence are not usually reproduced for anyone but the attorneys on the case and absolutely no one else.