I don't know if anything can be done about this, but when I used
Recurring Nightmare (returning
Bloodbraid Elf) he cascaded into
Grim Discovery, and that spell was able to target
Bloodbraid Elf. I targeted something else, so I don't know what would have happened.
A similar issue exists with things like
Demigod of Revenge; in certain cases you can end up creating an extra copy of the card.
Life from the Loam also does this sometimes. (I think on the 3rd targeted land, but I am not certain about that)