Messaging app is gone in 8.1?

Yup. I've been using it often when I was talking to my friends on Facebook, but now on 8.1 that app is just gone.

Is this the same with everybody? Why is it gone? Is it coming back, or is it gone for good?

Otherwise I really like 8.1. 8.0 felt kinda floaty, but this feels very grounded and stable UI-wise.