It looks like they were right. I’m attaching the Attorney General’s official November 4 summary of the proposed amendment, the text, and links to both. There’s no indication that the amendment would apply retroactively.

PROP 8
ELIMINATES RIGHT OF SAME–SEX COUPLES TO MARRY. INITIATIVE CONSTITUTIONAL AMENDMENT.

OFFICIAL TITLE AND SUMMARY
PREPARED BY THE ATTORNEY GENERAL

ELIMINATES RIGHT OF SAME–SEX COUPLES TO MARRY. INITIATIVE CONSTITUTIONAL AMENDMENT.
Changes the California Constitution to eliminate the right of same-sex couples to marry in California.
Provides that only marriage between a man and a woman is valid or recognized in California.
Summary of Legislative Analyst’s Estimate of Net State and Local Government Fiscal Impact:
Over the next few years, potential revenue loss, mainly from sales taxes, totaling in the several tens of millions of dollars, to state and local governments.
In the long run, likely little fiscal impact on state and local governments.

http://www.voterguide.sos.ca.gov/title-sum/prop8-title-sum.htm

PROPOSITION 8
This initiative measure is submitted to the people in accordance with the
provisions of Article II, Section 8, of the California Constitution.
This initiative measure expressly amends the California Constitution by
adding a section thereto; therefore, new provisions proposed to be added are
printed in italic type to indicate that they are new.
SECTION 1. Title
This measure shall be known and may be cited as the “California Marriage
Protection Act.”
SECTION 2. Section 7.5 is added to Article I of the California Constitution,
to read:
SEC. 7.5. Only marriage between a man and a woman is valid or recognized
in California. [Last sentence italicized]

http://www.voterguide.sos.ca.gov/text-proposed-laws/text-of-proposed-laws.pdf

I’m pretty sure in the description of the ballot measure I received that it stated it would apply to marriages regardless of where or WHEN they occurred.