Don’t underestimate a federal prosecutor. Perhaps we need a new saying: “If you give me six lines from the US Code, I can get a plea bargain from the most honest of men.”
In this case, hiding your chats is not exactly going to help you. If anything, it will be showing up prominently in the list of charges against you as destruction of evidence and impeding investigation.
For criminal actions in the US, at the least, what you do say can be held against you.
What you don't say cannot, and what communications you destroy (as part of an ongoing general "document management" policy, not as a specific response to a lawful demand for records) cannot.
However if you phrase your document management policy as "apply these guidelines so that our illegal activity cannot be documented by us as illegal" you will be having a Bad Day should that policy come before a prosecutor, Grand Jury, or court.
