If you suspect that your site content has been copied including adsense code how can you search for your pub- id? I realise that it might bring some income but if it is a bad neighborhood it could have an impact on your overall adsense income.
You cannot. But you do have a list of allowed sites on adsense where you can tell Google the sites that you do wish to earn from. That won't affect your income.
spot on!! if you are using allowed sites.. you will be able to see the sites name which are using your adsense code