Opened a few packs together, and was looking through each of the new cards slowly. Got caught up with something outside of the game and locked the screen. Came back and continued looking at them and they were still there. So I continued looking at them and got busy again. This was a while ago so I don't remember the details of when it bugged out and didn't have the time to bug report at the time, but I might have closed the app or it might have just timed out, but when I came back again, it threw an error and the game was temporarily completely broken I might have had to reinstall the app. I went to the deck builder and went to add some of those new cards to my deck and they weren't there, I checked the pack tab and the packs were gone. So it deleted the cards I would have gotten. They should automatically add to your profile when you open the packs not wait till you press continue or exit the pack opening. I know I lost at least 1 mithic and a couple rares this way. I'm on android by the way.