Trying to find the answer to this question.

[csziggy]

9. And there would be a paper trail

Which there was not.

I've read that NARA went through the memos and other paperwork they had and used that to identify papers that had not been turned over. For instance, if there was a log of who had access to particular Confidential, Secret, et al documents, but those documents were not in the papers turned over by TFG's White House office, NARA knew to ask for them.

Inventorying all that paperwork, then the boxes turned over earlier could be part of the reason it's taken so long to get to the point of a warrant, including all the legal steps that were taken to request missing documents.