Security carries teleport scrolls. If they can take one down, they can leave. Ione thinks she can read a teleport scroll, she's never done it and they fail destructively, but it's the sort of thing a third-circle wizard can do.
Probably they don't want to leave the interdiction zone, because then every god who cares to can send their forces after them, but they could hide in a (unscryable) house in a random place in the interdiction zone, for now, and she could get books from more places, try to find somewhere...