There is a bug with some of the Google Certification Program Exams where they are not showing in the advertisers accounts.
A Google AdWords Help thread has Google confirming the bug.
Googler, Bindu said:
Google Certification Program Exams passed between Dec 22nd and Jan 4th are not showing in accounts (also preventing some customers to see the certified status because of these missing exam.)
Please be aware that this is a known issue and this thread will be updated when resolved.
So if you have passed the test between those dates, December 22, 2010 and January 4, 2011, don't worry, Google will give you what you earned. It might just take some time.
Forum discussion at Google AdWords Help.