For future reference, you might wish to keep in mind that the rotation lock control and system sound control are really confusing. Originally, the side switch was used for rotation lock control (and a soft switch for system sounds) but IOS-3 changed the switch so that it controlled system sounds in order to keep consistency among IOS devices (a soft switch controlled rotation lock). Then, for IOS-4, Apple made a serious mistake in attempting to pacify some whiners that actually claimed that they turned auto-rotate on and off fifty times/day and consequently the side switch is mandatory. The result is real disaster.
The following is a C&P from a post made by Demo. It's a better explanation that I can come up with.
System sounds can be muted and controlled two different ways. The screen lock rotation can be controlled in the same manner as well.
Settings>General>Use Side Switch to: Mute System sounds. If this option is selected, the switch on the side of the iPad above the volume rocker will mute system sounds.
If you choose Lock Screen Rotation, then the switch locks the screen. If the screen is locked, you will see a lock icon in the upper right corner next to the battery indicator gauge.
If you have the side switch set to lock screen rotation then the system sound control is in the task bar. Double tap the home button and in the task bar at the bottom, swipe all the way to the right. The speaker icon is all the way to the left. Tap on it and system sounds will return.
If you have the side switch set to mute system sounds, then the screen lock rotation can be accessed via the task bar in the same manner as described above.
This support article from Apple explains how the side switch works.
http://support.apple.com/kb/HT4085
