I've noticed this during my last match on right node (supports yaay, spells meeh) of HoD and it's actually a favor for the player not against them.
Anyway, I've played with Ashiok, Nightmare Muse against Kiora. When I launched their first ulti, the three cards to choose from were two spells and Storm the Vault, I've selected StV due to the secondaries of that node.
When I openend my hand again, I realised that the card in my hand was actually "Vault of Cataclan", not StV, as expected.. after some mana gain I further noticed, that one mana is totally enough to get it casted.
It's difficult to recreate (and I didn't), but I don't think that the "stealing" itself is bugged. Instead I suppose, that actually all flip cards behave like this, it seems that the flip card itself has entered the opponent exile already with wrong side up. So actually everything that steals opponent cards should give you this results when it targets a flip card..
At least, the good point of the story is, that it didn't freeze my game and I really wasn't confident about that.
Happy Easter
I had this happen in the reverse during the Return of the God Pharaoh event.
The AI stole my Storm the Vault and the next turn dropped a Vault of Cataclan (they never cast StV)
I can concur with this issue. I stole a flip card using Ashiok's first ability. Had the flipped side in my hand. Have had this happen several times with Ashiok.
Hello guys, Sorry about the delay and thank you for your feedback! This issue is now under investigation.
Thank you for your patience, Marcela.