IF you really were doing nothing that would attract attention (and that would be more than just MSing activity. That could be cycling your CL, late payments, overspending your CL, or even sketchy BP providers) than you may just be an unlucky recipient of an audit that discovered your prior closure where they probably wanted to sever all relationships with you, and simply missed it. Finally, the audit may have revealed you to just be an unprofitable customer with a checkered past.

Whatever the case, it seems as if it was just bad luck that they found you. Sorry to hear it. You could try and contact them for the reason (which I doubt they will reveal) and perhaps plead your case that yes you were a bad person years ago but are now a reformed one who has toed the line and makes them money (if true )

Can't hurt.