Welcome to WebmasterWorld Guest from 184.108.40.206
forward 'em the first google email that you received, the one that acknowledged your report of the mistake, complete with all header information, and tell 'em to make it part of your permanent record, if they have such a thing, lol.
I'm guessing it's a followup email. If they haven't noticed one click here and there from me, they probably wouldn't notice one click from you. Really, I wouldn't stress out about it.
If I was you I would be pulling the ads from the site immediately.
But I don't think it's necessary to remove the ads. My rule of thumb is that Google want you to serve as many ads as possible, and expect webmasters to simply use the product as designed so that Google can handle the serving and targeting and tracking and auditing of ads.
They don't expect you to pull your ads whenever there's a discrepancy, or to use a click tracker to watch for attacks, or to block ads to certain countries, or to use the hosts file to prevent self-clicks, or to remove ads from low-CTR pages, or to stop serving ads after a user has clicked X times. And they won't penalize you if you don't. I'm not saying all of the above are bad ideas necessarily, but they're a little obsessive.