|Either you have jailbroken your device or you do not have a password set on it. Itunes will absolutely not access your device when it is password locked. Apple has set it up this way for security for the exact reason you are asking, so no one else can access your data.|
When you plug in a locked device the following message will show up -
iTunes could not connect to the iPad "name iPad" because it is locked with a passcode. You must enter your passcode on the iPad before it can be used with iTunes.
This is the message you see with an iPad, substitute iPad with iPhone for a phone or iPod for an iPod.