Yeah, i wouldn't worry about the 1 click accident. Shoot..My pet rat tramples all over my keyboard when he's searching for snacks i.e. crumbs in the crevasses of the keyboard. I'm pretty sure he clicked on a few ads a few times and no probs from "G" here.
I did this for the first time on Sunday. My mouse is playing up & I was trying to scroll to the top of the page & it wasn't behaving. Anyway, e-mailed G right away & heard back from them this morning, basically saying "thanks for letting us know, don't do it again". I ALWAYS close my browsers down when I leave the computer as I can guarantee if my toddler had access to the computer without me being around murphy's law states that she'd go on an Adsense clicking spree. So I don't give her access to my website.