sounds like it's just an immature fruit, not a plant with leaves?

I would keep it in water and see what happens. At the very least, you'll probably get a new plant from the top. I wouldn't expect the fruit to mature well.

Update.

After about a week of sitting in a bucket of water, some roots formed so I put it back in some dirt.

The pineapple has gotten bigger, so it looks like it's gonna make it.

Oh, so it WAS the whole plant, not just the fruit.