I received a duplicate mercenary Vandar card from a pack. Not a skin, not coins, but a card itself. Went to check my Vandar in the tavern and yes, I already had him with 28th lvl and with one additional skin, which is already chosen. Also, he has 25 coins, so the card didn’t convert into coins as well. Really disappointing to entirely lose a mercenary card for nothing and, I guess, this is not an expected behaviour.
Ugh… It’s an old and frequently asked question, see, for example, this and other references there. In short, you probably obtained Vanndar’s golden portrait from an event, or a ‘legendary quest’, allowing you to play with the mercenary, without actually getting his base portrait, represented as a card, which you have opened now, didn’t you?
OMG that might be true, I don’t remember, but it’s such a weird scenario. It is very unintuitive to show the user a card instead of a default portrait. Anyways, thank you very much.
Check out this:
https://hearthstone.blizzard.com/en-us/news/23765275
and especially this:
https://outof.cards/news/4425-hearthstone-patch-226-brings-tavish-brann-vanndar-skins-in-a-legendary-quest-chain/
If you have some of the other rewards, then that’s how you might have done it.
It’s actually documented and not unheard of, but it has indeed caused some confusion.
That’s how a base portrait is represented… Someone has written about it in one of the linked topics.