volume slider is missing

The slider volume control has disappeared from my iPhone 4s. I plugged it into my iTunes to download some music, then when I unplugged it, the built in speakers didn't work. If I use earphones, then the slider reappears... I saw some threads that said to clean the contacts with a Qtip or a toothpick, I did that and still doesn't work. The mute button is not on. Any other ideas?