Ok, some weird voodoo is going on. After a few more attempts, I slowly put the battery back in, gently put the tail cap back on, and voila! it worked again. To ensure it was not a fluke, I took the battery back out and tried it again, only to find that it did not work again. More research led me to find that if I put the battery in with the label to one side (the AW 17670 will fit with label on, but only in two positions, as if there is more room on one side of the tube than the other) it will not work, but if I turn it around, it works normally. Very weird. I examined the inside, and it appears that the green circuit board on the backside of the head has slightly moved, exposing some of the metal on the backside of the head. I have no idea if this is what is causing the issue, but it would make sense that after being left in a hot car for a day, the heat could have shifted the board, making the contacts not as effective, depending on battery position. Of course, cr123s are not effected by this. Very very weird. No more leaving flashlights in cars, even my beloved surefire lights.