As you've stated, everything says it shouldn't be able to happen. I
suspect either someone is giving out the wrong address (same as yours
but with a letter or two difference), or it truly is plain ole
phishing.
The inability to login when you inserted a "." proved nothing, as the
same help pages you're referencing remind you that you have to use the
"." pattern you created the account with to login.
It seems the troubleshooter pages have been moved so I can't find them
right now, but I don't think there was ever a good path for this
through them. Your best bet is to post to the GHD group
(
http://groups.google.com/group/Gmail-Help-Discussion) which is
staffed with actual Google employees.
Ockham's razor tells me there's probably a Daren.Miller, or
Darren.Miler, or even Daren.Miler out there.
Your best bet to prove wrong and have evidence for the Google Employee
to investigate with is to send e-mail to the first.last@gmail address
and request a response from a non-GMail account (like a free Yahoo).
Then, if it doesn't go into your e-mail box, and you get a response,
you'll have proof to provide Google.
--
Albert Camus - "Charm is a way of getting the answer yes without
asking a clear question."