After a second long phone call with a Vanguard rep, I found that the cost basis on my sale of VTSAX does reflect all my purchases back to 2006, even though they aren't covered from 2006 to 2012. The cost basis on my 1099 is a correct number that reflects purchases back to my first purchase in 2006.
Relief! I did not want to crawl in the attic and go through 14 years of paperwork to find all my purchases in that account.
So, I expect to have about $24k of other income, just enough to fill our standard $24k deduction. Then my total VTSAX withdrawal minus the cost comes to $78,872.
So I over shot staying in the 0% tax bracket by about $97.
The mistake I made was not making any Roth conversions in the 12% tax bracket.
Thanks for the scare to get me motivated to get all the info I needed.