I guess if you just check the stats, you'll see any rogue ones that never got paywalled as they'll show up as 0.00 earnings. You could just order the list by 'lowest earnings first', and that should show everything published before you joined the partner programme, with older dates, but anything more recent with 0.00 is likely to have the paywall button off, and you can then go in and change it in the story specs.