I haven’t entered the game for a long time, entered the arena, the key began to open, immediately, I received 2 gifts, a pack and 20 coins, but I didn’t give a coin to a pack
You did receive the cards and they will not have the new card indicator:
Arena prizes are added to your account immediately when the run ends.
Usually this happens at the third loss or twelfth win, but it can also happen when you have an unfinished run that is retired by Blizzard due to some external event (standard year rotation, special arena promotion, etc.)
In the latter case, it typically happens while you are offline, so you already have the dust, gold, and/or packs the next time you log in.
It’s confusing that you can go to the arena screen and “open” rewards that you already received, but that’s how it works. Turning the key and opening the boxes is only a cosmetic reminder of prizes you have already received.
Blizzard has also said that in some cases, pack rewards will be automatically opened and the individual cards placed into your collection, with no “new” indicator. I have no idea why they do it this way, because people will naturally assume that their cards went missing. But I assume they have a good reason.
Not true, in at least 99% of the cases. Perhaps even 100% if a bug that ahppened sparingly over a year ago is now fixed.
When an arena run is retired, such as when Rise of Shadows was released, the prices will be added. At least most of the time, probably all the time, the pack is added as an unopened pack. And it then goes unnoticed by the player who is busy opening the packs from the pre-release bundle and from the free promotion events that featured before and after release. They don’t notice that they open one more pack than they should have - that pack is the Arena pack.