My 4s used to have the exact same problem, no sound , no volume bar and so on like everybody says in this thread.
I had tried everything mentioned by our friends here but no luck.
First I thought it was from some physical problem. Brushing the dock with alcohol only helped a short while then it returned to no sound again.
BUT I FINALLY FOUND THE SOLUTION!!
Here are my steps:
- I had several backups prior to 7.0.3 update releasing. At that time when I made backup of 7.0 and 7.0.1 I remember there was no such sound problems at all. So I decided to rollback(restore) to one of my previous backups.
- I did not wipe any data before restoring. Just plug it to my PC and press restore via Itunes an choose the last known good backup.
Now my 4s is completely back to normal for 3 days so far.
Please try and let me know.