I don't think it's possible to get a Steam key from a purchase on the 2D Boy website. The only way you can get it on Steam is to buy it on Steam, or get it in a Humble Bundle (which is unlikely to happen anytime soon, since it's already been in multiple bundles last year). The Steam version only costs half as much as on the 2D Boy website though (and still includes versions for Windows, Mac, and Linux).

As for PMs there's no feature for that here, so...

I'm not personally sure, but I think it depends on when you bought it. If it was recently, they moved to the Humble Store, which as far as I know should provide a Steam key (I'm not completely certain, but I think they should). The Humble Store should send you two emails: One from Paypal (which only contains a transaction ID), and one from Humble Bundle (which should have your download link). Your download page would have a Steam key if they supply them.

If this was a while ago (before they used the Humble Store), then I have no idea.

im rather sure it was before the humble store, as the email only has a direct link to the http://2dboy.com/forum/ which is currently under construction.

Including a direct port(?) url to the download directory, the only reason i ask is so can rerun it so can do the steam achievements.

This was the responder of the email if able to clarify confirmation info.
World of Goo Mail Bot contact@2dboy.com via indie.indierevolution.org

Anyways, thanks for the info...