As of patch 26.0, cards from the collection have been disappearing. For example, Darius Crowley, Kor’vas Bloodthorn, Infinitize Maxitude, and several other cards.
Of the cards that rotated to Wild I have proof, I took screenshots. In the Wild decks those cards would appear in red and they do not appear in the collection.
There are 2 types of cards , owned cards and temporary loaned cards called Core
Patch 26.0 changed hearthstone year to Year of the Wolf and this created a Core cards rotation.
here text version
https://bnetcmsus-a.akamaihd.net/cms/content_entry_media/TVM7GYDSD9XB1679527943501.pdf
here image version
https://bnetcmsus-a.akamaihd.net/cms/content_folder_media/7A7R4LW04DPV1679514153567.png
If now they are missing and you can’t remove and re-add them this means you was using the temporary Core version and you was not owning a real version.
If you notice from links i posted there are some cards that joined your collection temporary for free as part of Core set … eventualy in a future hearthstone year this will be removed again and replaced.
edit: infinite maxitude is strange becouse is not part of rotation
Oh, by all means, do NOT post them here. That would only be helpful!