Why is the volume slider for my iPod Touch suddenly disappearing?

I have the iPod Touch 4G, it's fairly new and i've never done any damage to it, but recently the volume slider hasn't been showing up whenever I listen to music, youtube, or just anything. I restored my iPod, got the new update, and restarted it several times but its still not showing up. One improvement is that the volume bar shows up when I have the headphones on sometimes if I plug it back in, but it never works for the speakers. The volume only works for both when it's plugged in the computer, Is there anything else I can do to fix my glitchy iPod?