Found it! It is high in the passenger footwell up against the firewall. Sort of behind the center stack.
To get to it, remove the fiber cover that hides the fusebox (squeeze the two black fasteners to remove).
The filter is located left (inboard) of the fusebox. You should see two blue latches on the filter door, squeeze them together to release.
It's kind of a frameless pleated filter that fits fairly tight. I pulled on it a little, but didn't want to risk trashing it without a replacement so I did not remove.
Here's a photo. Sorry for the crummy quality. I shot it with my phone and a flashlight.