Running the Outlook Archive feature (auto or otherwise) should never create another OST, it will only create PST files. The OST file is created the first time you use Outlook and is just as you said, an exact copy of what's on the server (it's actually the offline version of the mailbox). So, either the PST file was inadvertantly saved somewhere other than the default location when it was created, or like you said it just glitched and never created one at all. I would be more likely to think it was the former, however.
