So I’ve been playing a few years now, in this course of time my cards have went missing. I don’t know why and would like this explained. One day they are there the next I open a chest and it says new card, when it’s a card I know I have already owned. Can anyone explain this for me?
May they went in one Earz and out the other?
More seriously, when exactly did this happen? If it was before the 4.6.5 Update (Nov '19), had you been disenchanting cards?
Did you accidentally make a new account, perhaps (were there any other changes?)?
Most recently it happened on my wife’s account with the new card “lasher”. It was a glory rewards card a few weeks back. Today we opened her chest and it said new card 
. Other cards I don’t notice until I open a chest and it says new, when it was already there.