Can my Apple Watch be fixed? The face fell off ?

Here is what it will cost in north America if it is at your expense....https://support.apple.com/watch/repair/service/pricing

Some posters have experienced battery swelling and say that was the cause of the face falling off. If the watch is less than one year old it is under warranty, and you should discuss this with an Apple Specialist by clicking on the "Contact Support" link at the top of this page.