Like many who are used to iOS, it is a habit to unlock the phone by swiping from left to right at the bottom of the locked screen. The bottom of the screen is where the unlock slider is located in previous version of iOS.
In iOS 7, Apple replaced the unlock slider with the text “> slide to unlock” at the same bottom location. You can however slide to unlock from anywhere in the locked screen. As long as iOS can detect a left-to-right gesture, anywhere on the screen, it will unlock the phone.