Papers aren't debate. And I presume they had a warrant.
You're the one who's confusing the issue. Some constitutional questions are complicated and call for deep historical knowledge. This isn't one of them.
The Supreme Court disagrees with you.
They are protected if they are "integral part[s] of the deliberative and communicative processes by which Members participate in committee and House proceedings with respect to the consideration and passage or rejection of proposed legislation or with respect to other matters which the Constitution places within the jurisdiction of either House."
Such papers were taken and examined.