Hi all, just to give you an update on this. I've called several dealership service departments and they were all stumped. One place hung up on me, another pointed me back to the general area of where the passenger side fuse box was... I said yes i know where the box is, I just need to know the fuse number for the low beams as it's not indicated anywhere on the panel or manual. I could feel him shrugging over the phone. Another dealership was more helpful and checked very thoroughly. Ultimately he advised that there's no fuse for the high/low beams for the lr4. The wiring diagram just points it back to the fuse box and it's connected to the main board there.
So... In case anyone experiences both lights out, you now know it's not self serviceable and you'll need to bring it in.
As for me, it turns out I had a bad relay on the HID harness. But this was a good lesson learned.