If your verification file or meta tag is still present on your site, try clicking the "pending" link on the My Sites page and then clicking the "Verify" button on the Verify page. We reverify periodically and generally this is done in the background -- we find the file or meta tag and the site remains verified. However, every so often, this reverification process is pending, and clicking the Verify button requests the reverification check right away.
If this doesn't work, please post back with your site URL so we can check into it.