So, if you unplug your headphones while listening to a song, the iphone will think that the headphones are still plugged in. This means your phone will not ring and you can't hear anything when you try to talk. Kinda frustrating to say the least. Change the volume with the side volume toggle and if it reads "(headphones)" by the volume setting, you have the bug.
The fix is to plug the headphones back in, go to the ipod area, stop the song from playing, go to a different menu in the ipod player and then go back to the main menu. Then you can unplug the headphones and reset the glitch.
That should do it.
If you left the house without the headphones or the $20 Griffin adapter (for gen 1) you are shit out of luck I guess. Way to design a recessed 1/8" jack apple.