My iPhone ringer disappeared?

I don't know what happened but after I unplugged my iPhone 4S from the charger, the ringer bar disappeared

Try plugging in some headphones to see if the volume bar restores. If so, exit with the home button while they are plugged in and things should be back to normal.

How do I get my volume bar back on iPhone 4?
https://discussions.apple.com/...ad/3520733