Go back and stand near Terenthis. When someone else turns in Escape Through Force/Stealth then the NPC will spawn and be available for few minutes. Anyone eligible can take the quest (level 15 or higher).
Read the Wowhead comments on the details of her behaviour…
Well, I have taken 5 alts through the quest chain in the last few weeks, it does. Really. Passing through, I not infrequently see the NPC standing there. Occasionally see “her” running into the area or leaving.