I’m having the same issue. This is also the second time it has affected me. Last time I lost cards while not playing for a few seasons, so I did not report it and just repurchased them. This time though, I don’t have the dust. Some of them are part of new decks I was excited to build with the new expansion. I hope I’m able to get them back somehow.
Thank you very much team; for looking into all these bugs, and making the game as great as it is! <3
I have this issue as well - many legendary cards that were part of my decks - now missing and saying I need to recraft them. Do I submit a bug report or is this somehow expected?
Which cards are missing? If they were removed from core set then this is expected.
Drakkari Enchanter is missing and it’s in core now…supposedly, and I had already done the tutorial to earn both enchanters.
Dear Hearthstone Support Team,
I recently logged into my Hearthstone account and noticed that several of my cards have disappeared. Among the missing cards are Zola the Gorgon, Kalimos, Primal Lord, and several other epic and legendary cards that I previously owned.
I am certain that these cards were in my collection, and I have not disenchanted or removed them myself. I would appreciate it if you could investigate this issue and help me recover them.
Drakkari Enchanter is not part of the core set, albeit she mistakenly appeared there for a few days. A list of all cards that entered and left Core is available here.
Those were core set cards
Cards that you did not craft and were given access for free for the year.
The core set just rotated and some cards have been removed and new cards added in
You can read the article linked by Vyraneer above which includes this graphic resume of the core set changes :
https://bnetcmsus-a.akamaihd.net/cms/content_entry_media/0OEPTFZ0757W1739224158613.jpg
If you check your collection you will notice that you now have access to Krag’wa the Frog without ever crafting or opening it in a pack (for example)
A lot of my confusion comes from being a Wild player. I don’t stick with the core set, so I shouldn’t be missing anything I had yesterday, right?
I’ve also noticed, along with some of those previously mentioned, that I’m missing Dragonbane 2 Overdrafts. I also have a distinct memory of needing to rebuild Lord Marrowgar after a previous patch; and that’s a card I’m pretty sure one just receives with the Death Knight tutorial, no? I come and go on this game, so I’m a little confused with the standard decks that just appear in my collection, and sometimes fall apart with set changes like this. 
Check the link I’ve provided
Same thing but from previous rotation
https://bnetcmsus-a.akamaihd.net/cms/content_folder_media/N68NFIECFYBX1707418383158.png
Perhaps what I’m failing to understand is what it means to be part of a core set. Does that mean that for a period of time, I was given a copy of Lord Marrowgar that I could not keep? A card that is not part of the basic set, but just offered to all players (but not to keep) for a certain amount of time? Just trying to understand.
yes thats exactly right, they loan us cards to use for free for 1 year, then at the end of the year we lose some of those cards and then gain new ones
Yes, exactly.
20chars
I am encountering this issue too! For example my Wild decks that had Alexstrasza, Metamorphosis, Sylvannas Windrunner, are now showing missing cards.
And did you read this whole thread to see that there is no error, and the missing cards are due to Core set rotation?
You did not own those cards; they were only on temporary loan from Blizzard.
Me too. I’m missing a golden Zola the Gorgan and Bladestorm. I opened them at the time they came out in their expansions, and they weren’t dusted. This happened last time they removed core cards and I lost some wild cards. I loathe this new feature. 
Are they missing from a deck, or from your collection?
If they’re missing from a deck, that means when you built the deck, you (perhaps unknowingly) used the Core version. Even though the Core version of a card is functionally identical to the original, it still does count as a separate card. Simply edit your deck and replace the now-missing Core cards with their original expansion set versions.
If they’re missing from your collection, then either you never owned them in the first place, or they’re really not missing at all and you’re just using the search/filter function incorrectly.
This feature isn’t new – it was introduced in 2021.
Also, I don’t understand why you would “loathe” it. Blizzard loaned you some cards for free. What’s not to like about that?
I appreciate the enthusiasm, but yes, I did own them. I’ve had both of those cards for years.
Then you still own them.
At worst, you have to update a few decks to replace the Core version with your original expansion version.
What is the actual problem here?