iPad freezes in lock screen after a defect multitasking gesture

When water spills on my iPad, the water confuses the iPad that it's a finger and you could pinch with one finger. If you don't know what that means, just ignore it. All I'm saying Is that my iPad's screen was completely dr when it happened.

I was at the Facebook app and then I pinched to home with 4 fingers. But the Facebook app didn't dissapear completely. I can still see it, transparent in the middle of the (lock) screen, with the size of the screen of a previous generation iPod nano.

Immediately, I locked the screen. When I pressed the home button, the lock screen was no lock screen at all. The clock's up in the status bar, I'm not seeing the 'slide to unlock' and I can still see the almost closed Facebook app. Also, I can't pull down the notifications nor pull up the control center. I can't restart or reboot the iPad. The red slide to turn off doesn't appear no matter how long I press then hold the power button.

The iPad is turned on the whole time i'm typing this and it was set to turn of display in 15 minutes and it did just that right now.

I can still use Siri, or rather summon Siri. When I hold the home button, Siri comes up, but when I seached for the web, Siri prompted me to unlock iPad and type in the passcode. The rings around the numbers where a little jaggy. When I did typed the right password, it brought me back to Siri. I can't reboot the iPad using Siri.

I can't do anything else.

What should I do? Just let it drain the battery(still at 60%, I made the screen brighter)? That's all I could think of right now.