Why is my iPad 2 half in half out of an app?

I was texting a friend, then I closed the app—the five-finger way of closing an app (putting five fingers on the screen in a circle and bringing them to a center point). My screen got caught half-in and half-out of the application. I've tried everything. I've tried shutting it down, but that won't work. When I turn it off and then press the power button to turn it on, it doesn't even go to the lock screen! It just goes to the glitched app! My background is behind the app, in case that helps, and the back moves when I shake the iPad (like it does normally). My screen works, because I have the three-finger tap zoom on, and it works!!! I have never spilled anything on or near it. I dropped it two years ago, and the sound buttons is a little mushed, but it works. This has been going on a long time, but it have always been able to get out of it by pressing the home button.

Please help, I love that iPad and I have a lot of information on it!! Thank you!