Hopefully Nexon catches this quick.

This is what happened with tradeable cloud stroll chairs; their data was removed (or overwritten) with the sengoku patch and the chairs were just deleted from inventory.

I'm surprised they have it set up to handle gracefully. I know that there was something like them removing Monster Familiar data in JMS and that card would crash your game if you looked at it. I don't remember the specifics, because it didn't happen to me, but I know it included crashing due to them removing data.