Firstly it is always good to know the history of the phone especially when it comes to audio problems.
· What was the phone doing before the sound stopped?
You should have left the audio IC alone as you have just created a variable in your repair. The audio IC decodes and encodes the sound, since you said top speaker was working I would be looking at the speaker amp components.
You need to diode the dock connector there are filters near it that could have been nudged or blown. Check for open lines on the speaker amp circuit. If you have ruled out parts that is where the problem should be.