Originally Posted by Mike-in-Orange
Have you tried repeating the process that got you out of sync in the first place - ie locking the car with the fuel door still open? Sort of grasping at straws here because I find it a bit odd that this would even happen in the first place. Just as the doors are either locked or unlocked, I would think the fuel door would be the same regardless whether it was open or not when the locking mechanism engaged.
Okay, mystery solved:-) I went and rechecked everything. It turns out that when I put the cap on, I'd left it in a position where the raised portion you grab with your fingers to put it on and take it off was vertical and that was interfering with whatever little detent mechanism keeps the door closed when you push it down. The interference was just enough to make the door pop open when I unlocked the car.
Thanks for the ideas, folks.