If McCain cares about Energy, why was he the ONLY Senator not present to cast his vote?

Did you know that you can save fuel and run your car on water

David S asked:

Sen. John McCain missed two critical energy votes on H.R. 6, The Energy Independence and Security Act, in December 2007. These votes – on December 7th and 13th – would have stopped debate and allowed a vote on an energy bill that included critical tax incentives for renewable energy sources – a bill to strengthen national security, lower energy costs, reduce global warming, grow our economy and create new jobs, and increase American energy independence. These votes were critical to making a $21 billion investment in clean, renewable energy and energy efficiency, including a $3,000 tax credit to help working families afford fuel-efficient plug-in hybrid and electric vehicles. On the morning of December 13th, Sen. John McCain was the only United States Senator to not vote on this measure.

http://www.autobloggreen.com/2008/06/24/is-john-mccains-300m-battery-prize-a-good-idea-pelosi-chimes/

Did you know that you can save fuel and run your car on water