Gen. Flyn is a top level military security officer....would he not make his own recordings of important conversations...?
What if he knew the exact details....and as soon as the FBI started on about the phone calls Gen. Flynn was aware of the trap.
This was passed off as a routine matter, as part of the trap.
Remember how Comey bragged about how he could not have "gotten away with it" except it was just a few days into the administration, while they were still getting their feet on the ground?
The entire point is, it did not matter what General Flynn said, if the FBI was willing to falsify documents to get him fired and/or convicted.