Qui Gon isn't as "high" a master as Yoda or Obi Wan.
Why do you assume it's the SAME X-Wing? Ya think maybe there's more than one around? Besides, he flew it to Cloud City, so it was still there.... right? Why couldn't he, or someone else, have just retrieved it? The Empire's forces were run off or else Lando, Leia, etc couldn't have gotten the Millenium Falcon back.