Assuming you're referring to the Android Quick Settings panel, there are a few ways to get it back if it's disappeared.
One way is to swipe down from the top of your screen with two fingers. This should bring down the Quick Settings panel regardless of where you are in the operating system.
If that doesn't work, go into the Settings menu and look for the Display category. In here, there should be an option called Quick Settings Panel. Make sure this setting is turned on.
Finally, if you still can't find the Quick Settings panel, try restarting your phone. This will usually fix any minor glitches that might be causing problems like this.