You may need to log into the Support Center - and then in the black navigation bar across the top - you'll see "Check Your Existing Requests".
Click on that, and then all of your Open requests will be detailed. You may need to click the small "Compact List" link in the right side area to see all the open requests. Then click on the subject line and you'll be into that ticket. Scroll to the bottom to add an update, attachment, screencast, etc.
To the right of your Request page, you'll also see a link that shows your Recently Solved and Closed Requests. The ticket you are looking for may be in the Recently Solved list.