It looks like it was a sting op.
Covington lawyers were the patsies. Eric Holder connected with Covington. Holder connects to Obama, etc., etc.
The thing we don't know is who was in on the sting. If, for example, they needed a doctored 302 for evidence down the road, then a white hat agent may have been part of that to make sure the notes were conducive for altering. So maybe Pientka is a good guy whose job it was to get the job rolling. That would explain, also, why the 302 is "lost". It's evidence. Good guys holding it means bad guys don't really know what's in it.
Same with Wray withholding exculpatory evidence until now. It could be it was done because Wray is a good guy and didn't want to give the sting away.
Too many angles here for anything conclusive at this point.