It seems the best you can do is quote from the original double miles offer. Also, in your post, you don't mention whether you talked to a supervisor--if you haven't, call back and ask for one.

Here's a link to a page with all of CO's recent press releases:

http://www.prnewswire.com/micro/CAL

The one from Nov. 5th should be the relevant one to quote from. It says:

HOUSTON, Nov. 5 /PRNewswire/ -- Continental Airlines (NYSE: CAL) is
offering double miles for its OnePass frequent flyer members traveling on
Continental between Nov. 16 and Dec. 15, 2001. This special double mile offer
is good for all Continental Airlines, Continental Express and Continental
Micronesia flights systemwide.
OnePass members residing in the U.S. must register for this offer by
visiting continental.com/onepass or calling 1.800.346.6090 and providing their
OnePass account number, zip code and promotion code 50099. Bonus miles do not
qualify towards Elite status.
Continental Airlines' OnePass frequent flyer program has won more
InsideFlyer Freddie Awards than any other major airline, including "Best
Elite-Level Program" 11 times out of the past 12 years. The OnePass program
also received the "Best Award" in recognition of reduced miles from the U.S.
to Latin America, as well as "Best Web Site" for 2000.
Continental Airlines is the fifth largest airline in the U.S., offering
more than 1,900 departures daily to 122 domestic and 89 international
destinations. Operating hubs in Newark, Houston, Cleveland and Guam,
Continental serves more international cities than any other U.S. carrier,
including extensive service throughout the Americas, Europe and Asia. For
more information, visit continental.com .

So, assuming that you registered for this promotion, it is unmistakably clear that you deserve double miles for your Nov. 18 flight activity. Good Luck!