Well, one thing you can do is check with Prometric's site that they maintain for such things,
i7. It will mention if they've mailed the certificate to you, and will let you verify if they have your correct address.
However, you also didn't mention where you are, so that could affect it - it sometimes takes a while for certs to get to non-US locations. If you're really that concerneed, after checking i7, you can email
[email protected] to ask them.
Hope this helps.