If you wish, you can turn the knob connected to the battery lead in the opposite direction from where it is now, which will "disconnect" the battery from the car's electrical system, then recharge your battery in place. You will likely need to open the trunk the old-fashioned way, with your key. The keyhole is under the chrome strip on the trailing edge of the trunk lid, centered and facing down towards the ground. It can take a bit of muscle to get the lock to disengage. It almost feels like you're going to break it, then it gives way, at least that's how mine acts. Try to remember not to open the car doors when the car has no power, as the windows will be unable to move down as they normally do when the door is opened.
I think there is an electrical drain on our cars beyond that which you would normally expect, exacerbated by going in and out of the car without starting it, causing the F1 pump to prime, etc. My guess is that it may have been more than a week since the car was started. I experienced a dead battery recently myself, and couldn't find any particular reason but lack of use. Good Luck.
