Ok, doing that was a silly mistake, but it could have been prevented by:
1. excluding the present release from the search result when looking up a destination release title to move the discid to, or
2. not allowing the move to proceed if the original and destination discs are the same, and give the editor an error prompt instead, or if not
3. nothing should happen, ie the edit has no effect.
My bad, but could this be fixed?