The information that you are looking for exists in this article that you were reviewing earlier 👉 If your Apple Watch is lost or stolen
I understand that your Apple Watch Series 6 has been lost and the battery is dead. You stated that you have tried everything in the Find My app to find it unsuccessfully,
Since the battery is dead now, there is no way for the Apple Watch to report its location. You will have to find that Apple Watch manually by physically looking for it. Apple is not going to be able to find it for you.
Axel F.