Yeah, I'm a bonehead. I had the RCAs plugged into the "phono" input instead of the "CD" input on the receiver. That's what I get for hooking it up in the dark!
I have noticed though, that the phone is still sensitive to how things are hooked up. If I plug the headphone jack into the phone after the receiver is on, the "headset" icon usually comes up instead of the "headphone" icon, and it results in some very peculiar behavior from the phone (my internet radio app automatically launched, then crashed, and other odd things were going on also). If I plug it in before I turn on the receiver, I get the "headphone" icon most of the time, and other than having incredibly low output, it seems to work ok. I'm guessing that the phone senses the different input impedance of the external device to figure out what the device is. I know my laptop works similarly, and will adjust the output based on whether it thinks it's got headphones or a set of powered speakers connected.