1) Add Spell Scroll set to Slow in map editor.
2) Play the scenario. Pick up the Scroll. Check the hero screen, the Spell Scroll contains the Slow spell, the Slow spell is writen in the hero's Magic Book.
3) Save the game.
4) Load the just saved game. Check the hero screen, the Slow spell is replaced by (null) in the Spell Scroll info text, the Slow spell is not writen in the hero's Magic Book.