Why is there a spring in the bottom left oh my 2ds xl?

I opened up my 2ds xl after it fell into a dog water bowl almost a year ago. The orange light comes on to signal it’s charging but the screen won’t turn on and the blue light won’t come on either. I’m pretty sure it needs a new battery, so I’m not concerned for that. I’m more concerned about the spring that was in the case when I opened it. That’s where it was and I’m not sure if it belongs. Help please?