Fantasy prison would indeed happen, because the patron of the Silver Blade would certainly come find you!

Aeryn is a high level sorceress, and would certainly want to teach you a lesson first . . . so if you'd like to tangle with her, risking stealing the jewel, you can do so! You will lose the encounter, get your ass suitably kicked, however, adn then wind up in a dirty prison with a relatively modest bail of 250 GP, and Aeryn's eternal disfavor.