Let's also remember that Jo'Bril was an extremely flexible lifeform. His ability to fake death might translate to an ability to fool all sorts of detectors and sensors that would normally block access to the shuttles.
Indeed, it might well have taken Crusher more time to secure access to the modified shuttlecraft than it took Jo'Bril: a ruthless and experienced criminal would have an advantage over an honest Starfleeter in that respect.
What I find especially enjoyable about this episode, in reviewing it as a result of this question, is the Ferengi Death Ritual thing. Picard and pals apparently think the body must not be violated because it is on its way to a decent burial. But DS9 makes it clear that the idea rather is to preserve the body in mint condition so that it can be cut to pieces and sold forward to collectors...