I've seen this issue on the latest release for PC and web, and been told that my computer was at fault, despite 8 GB RAM and reasonable performance.
Now the same thing has occurred under the latest version of iOS on my iPhone 6 running the latest TestFlight beta version:
I'm playing Quickmatch and from time to time my opponent will play a card, but its image is not shown to me. I see the back of the card as though it was an un-sprung trap. Sometime the card can make it to the graveyard and remain there without revealing its identity.
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