I have the same problem !!
cards from the various sets are missing, also recent/standard expansions: forgotten realms, strixhaven, kaldheim, zendikar.

Both those purchased in physical stores and those obtained in the game.

I am definitely missing cards from my collection, for example I am missing Scourge of the Skyclaves (not to mention others), but there needs to be some sweep that checks. I can list a few I know I am missing but who knows how many others have left my collection this way.

I notice this happens every time I download a new card set for a new release, not sure if it happens other times. I haven't gone through my decks to see what is all missing but I know I had the common blitz leech because I play a flash deck for fun sometimes, and had it in there- but then took it out. Opened some packs today and had the "First" text glowing ontop of a blitz leech common, so for certain cards are being removed from peoples collections at random possibly during new set launches.

This is not the first time this has happened, I have lost uncommons, rares, and mythics this way.

It's not just cards not being put into your collection from opening packs, cards are being removed from collections as well.

This bug will kill this game in time.

Missing cards as well.

Played MTGA at launch for a couple of weeks , crafted a bunch of cards for token decks and vampires and knights. Came back to it a couple of days ago an the decks I played before are now half full with missing cards. It says I don't have any copy of "raise the alarm" as an example, which must be a joke. It is one of the most common commons... And I'm missing rares and mythical too... Thought I could have some fun in historic games... Got disappointed

Yo...i just bought 10 packs and got 2 cards i was wanting to add to my deck. When i go to find them they're not there. PLEASE HELP!!!

I opened a pack that I have just received, I got a card called Ledev Champion. I was excited to put it in my deck, it was not found in my cards list and I cannot find it anywhere. Am I doing something wrong? Please advise, I have had this issue with a few decks and cards I have received please HELP!!!

missing 2 copies of Lurrus of the Dream-Den that I received as ICR & from opening a pack. Also missing at least 1 Zenith Flare so who knows what other cards are missing.

Gotta love pulling a Planeswalker and a few Mythics and then not having them after. Why would I spend money on a game with the chances that 50% of the time I pull a card I may not actually get it?

I made a list of the lost cards (missing cards from collection), and it's far from what I expected to be, I've lost a total of 276 cards! I have some lead of what is preventing cards to be storaged in your collection. I hope people with this issue can confirm if their cause might be the same.

◉Theories why the cards that you get from drafts, packs and daily rewards are not kept in your collection:

-Maybe it's due to a connection error that prevents cards to be registered in the server even your victories/loses, daily/weekly wins and store purchases are properly tracked. That connection error might happen if you alt/tab your windows, i.e. switching Arena window to Chrome in order to choose a song from YouTube or check social media.

-It also might be because you're using a laptop, and when you plug/unplug the charger, the laptop disconnects from internet for a few seconds (1-3) (they have a energy saving program that triggers automatically even if it's disabled, that manages and switchs perfomance according if it's plug or not).

-And finally, my last guess, might be because the use MTGA Assistant, which displays overlayed in the game, and might affect the MTGA's connection.

I have experienced this myself , opened a booster and got Crux of Fate, Immediately went "Ohh I kinda wanna make a dragon based deck now!" and when I went to the deck builder the card just did not exist no matter where I looked.
Honestly if it can't be guaranteed that the cards I pull out of boosters are going to actually be in my inventory, I will never spend money on this game.
If I don't receive the product I am paying for, you are stealing from me.

a good half of cards in the main deck that i use are missing, i know i had them for a long time but the game claims i never had them? where did my cards go..

I also collected "Krosan's Grip" today as part of the mastery pass, and can't find it in my library to save my life.

The same has happened to me with Mizzix's Mastery and Crux of Fate.

I literally have unpacked two cards in the same hour (Its happened before and until now I legit couldnt find a support place to talk about it cause im missing like a couple hundred cards) and i meant both a them are kinda busted ngl, a red white two drop that burns for three and gains me two life in the new strix art, and then later I pulled day of judgement in the new strix art and I can't find them no matter how hard I search through my collection

I have recently collected 'ephemerate' and 'Krosan's grip' - but htese are not in my colleciton. Moreover, when I include the 'not collected' cards -they don't come up at all [i.e. they appear to be missing from the game itself].

I got "Teferi's Protection" as in a reward pack for strixhaven quickdraft. But when I went to include it in my deck it had disappeared.

Today i used the code for the preconstructed deck “critter corps”, which, for example, contains 2 selfless saviors. Before entering the code i already had two saviors in my collection, but When i got the deck the number of saviors in my collection still is 2. Same thing for “ozolith”, “fabled passage” and others…
I don’t know if this is normal

“I believe I have come across some type of bug in the card database

There are cards that I should have available but I cannot add to my deck, they will not appear and deck building mode.

These cards are not on the band list, should should be available. As I have made purchases this is a slight inconvenience and actually hinders me, as I need the cards to be available”

I am having the same issue with Teferi’s protection

Teferi’s Protection Bug..........

I drafted Teferi's protection and it just vanished when I went back to my library after completing the draft.
And yes I played it during the draft.

What do we do than?