A while ago I noticed that I didn't have a rear channel in my Corolla's stereo setup. After a lot of digging this evening, the culprit is the STD/NTW swtich on my head unit.
Standard uses the outputs on the rear as Front, Rear, Subwoofer.
Network uses them as Front, Bandpass, Subwoofer.
Now I have a rear again, Yay!