My iPhone thinks it's always docked -- Volume slider disappeared with no audio output

EDIT3*

I managed to fix this problem in a risky way, but it worked for me. Read below.

Pin 11 apparently carries out the following function :

11   GND     
If connected to GND the iPhone sends audio signals through pin 3-4
otherwise it uses onboard speaker.

Source

My iPhone is stuck at the function of using an onboard speaker (dock), and only produces sound when connected to a dock or a charging connector. Whenever I take it out, the phone mutes itself except for ringtones.

I am guessing that some switching mechanism is stuck at that setting. Does anyone know if there is a specific pin-like switch that needs to be adjusted to fix this ?

EDIT

I noticed that sound only plays when connected to the charging dock and powered on. Using the cable with no power OR without the dock mutes the phone. If I remove the iPhone from the dock while it's playing music, it continues for a few seconds and then mutes, the music player is still running on play, but with no audio output.

EDIT2

When trying to connect the AppleTV, I found the following evidence that shows how the iPhone thinks the dock is connected.

The iPhone was NOT docked at this time.

I've fixed this exact problem by clearing out pocket lint from inside the iPhone dock connector with a paper clip. Hope that helps..

I found a method that worked for me. If you're having a problem similar to mine and cleaning the dock did NOT work for you, try this at your own risk. Disclaimer : This method might permanently damage your iPhone, mine is out of warranty so it wasn't a big deal if I damaged it, I would still need to pay for replacement.

I don't know what may have caused the phone to lock at the docked state, but my first thought is that there is a switch mechanism inside the dock connector. All I did was get a key and jam it there, and rotate it a bit until it got fixed.
Note: If I inserted the key there and did not rotate it, the problem is fixed temporarily until the key is removed. The only way I got rid of the problem completely is to rotate the key and push the pins downward.

If you try to insert the key and remove it, the problem still persists. I had to jam the key in deep and rotate it a few times (gently) to permanently fix this issue.

Make sure you insert the key in the middle - left part of the dock connector, that's where pin 11 is located (I think).

After placing my phone on a dock again, I lost control over the sound. I did the same method with a bit more rotations using the key and now the problem is gone 100%. Not sure how, not sure why, but it worked.

If using a Key seems too risky for you, read below

Use cotton wool from the end of a qtip (but not the qtip it's too wide to go in) use a nail file or a very thin screw driver to put the cotton wool inside the docking part and gently move back and forth. If you use alcohol even better.

(PS i tried a lot of compressed air and a toothbrush and it didn't work - the iPhone was about 3 years old so it was filthy inside. The cotton wool came out surprisingly dirty - ie the tooth brush and the compressed air will work if it's a little dirty or there is a little bit of lint - but not if its very dirty.)

Good luck.

When I see this issue, it is usually because the dock connection has liquid damage. Check for a rectangle near the pins. It will either be white for no liquid contact or a pink/red color indicating liquid contact.