The requirements for citizenship are also that you have been without immigration time restrictions for the last 12 months before your application. In EEA terms, this means having PR for 12 months.
Read section 2.4 of the
application form for citizenship (Form AN). It requires you to list the ways in which you qualified for EEA residence, if that is what you are relying on.
Documents issued under the EEA Regulations do not confer status on you: they confirm what your status is. To my mind that means that just because you received a documents saying you had PR, that does not mean that was the case.
The grant of citizenship is discretionary. I think that if you apply based on a claim that you acquired PR last year, you will likely lose your application fee.
I think that you will satisfy the eligibility requirements in January 2013.
In addition, if you want to rely on having retained the right of residence, then you may want to ensure that you ask UKBA to issue you with the correct paperwork. Otherwise you may find that you have to supply evidence of your ex-wife's exercise of treaty rights from 2007 - 2010, as well as yoru own work etc. from the date of divorce until you (actually) acquire PR in January 2012.