I don't know, but I DO know that you need to plug it in very firmly; I thought that it was broken when I only heard sound from my left earbud. False alarm; I just didn't push it hard enough.
Doesn't show up in dmesg on my Ubuntu laptop either. Test is inconclusive. If the Pandora uses alsa (which I assume it does) then theres likely a command that can be issued to find the state of the headphone jack. I'm not having any luck finding it however. Will post back when I do.