Following these Berger threads, I get the impression that CNN floated the "socks" story well ahead of Fox, then squashed it after Fox and Rush picked it up.
Your theory makes sense: notice that Lanny Davis' comments focus entirely on denying that Berger stuffed docs in his socks, not on taking the documents themselves.
Since where Bergler stuffed them is now a point of deniability for the Dems, I'll bet the Feds do have a tape.
The fact that Lanny is out is a leading scandal indicator