2008 Altima Coupe 2.5 MT

I have a PO146 code - Bank 1 Sensor 3
This is a problem with the second (and last) downstream O2 sensor after the Cat.
I'll be darned if I can find it.
Has anyone replaced this part (Denso 234-4382) who can direct me to it's location on the exhaust system?
While I've seen references to it possibly being covered by a heat shield on some Nissan models (which is why I may be missing it), I've also seen it referred to as "after HC adsorption catalyst (Under floor)" on others, making me wonder if there's some kind of access from the car's interior. I really don't want to start tearing my Altima Coupe apart blindly searching for it.
While there's plenty of info online on testing this O2 sensor there's zero descriptions or diagrams of where it is on the car and how to access it.
This particular sensor only monitors and does not control anything, but I'd rather fix it than just clear the "Service Engine Soon" light with my diagnostic tool.
Any assistance would be greatly appreciated.

Common mistakes when diagnosing the P0146 code

Follow these simple guidelines to prevent mistakes:
Do not assume the O2 sensor is bad by replacing a good part; do a complete pinpoint test.
Check the mass airflow sensor for proper operation and contamination from dirt, oil and debris from a compromised air filter or an oil bath type filter.

2008 Altima Factory Service Manual

Okay, so it looks like sensor 3 is after the resonator, but well before the muffler, which means it has to be out of sight under one of the 2 heat shields. That explains why I couldn't spot it on a quick visual inspection.
Thank you very much for narrowing down the location for me. Looks like it's going to be a real PITA to swap out!