It'll become apparant in the comic later, but the Zha'Tahn are like the ancient Chinese, who considered their culture the "Middle Kingdom" or the Greeks who regarded all other cultures as "barbarians"---extremely ethnocentric---they think any other creature would think it an honor to be made into a Zha'Tahn, and literally cannot conceive that anyone would want to escape from being a Zha'Tahn. So, when they notice Lafferty/Flickerflame is gone, they'll think he's a lost child, not an escapee, searching accordingly--and not search the shuttle.