iPhone: no sound

This morning, my trusty iPhone MyPhone greeted me with unaccustomed silence. The standard troubleshooting tips did not work! After beating my head against the wall for a few moments (to wake up), I Googled myself out of trouble:

1. Check the standard troubleshooting tips in Apple's official iPhone User's Guide. Do this first!
   
2. Click the Settings icon
3. Select General.
4. Select Reset.
5. Select Reset All Settings. The UI (SpringBoard/SummerBoard) restarts. If you have a passcode, you are prompted for it.
6. Sound re-appears.