You might just have broken the backlight fuse. Try to look at the screen using a flashlight when the ipad is on. If you're able to see that the screen is displaying something, then it means the fuse is burned. It is possible the bypass it by putting a little amount of solder. But for that you pretty much need a microscope.
It sticks right behind the camera itself, you need to separate the camera and the ribbon a little. But be careful to not separate it to much or you'll break the ribbon. Honestly tough this sticker is not crucial and even if it's not there the camera/light sensor will work just fine. I think it serves as a ground to avoid or lessen screen static.