Sorry James. It's nothing to do with luck. Once you've left, immigration don't care. In the golden era of the OA visa (before the insurance headache) no-one ever went to immigration, no one did TM30s and 90 day reports and no-one ever got fined. Once again, the fear-mongers are out in force.
Will never be picked up. I've done it myself over the years if I've been leaving shortly after the 90 day report is due. Once you've left and come back they really don't care about old TM30s and 90 day reports