Hm... I actually ran into something similar to this earlier, where a Missile Upgrade replaced the Fireball. Missiles are aquired through a <EVE0030 jump to a global event, so the rest of the Santa event didn't play and <FL+0241 was never set. However, I changed it so that the Missiles should never replace any items which are acquired in the middle of an event, so that shouldn't have happened to you.
Although, it's not totally clear to me whether this actually happened to you, or if you were just anticipating it because you didn't have this Fireball?