Oh No! I hope she gets him back. I lost a tiel and I wouldn't wish that on anyone.
Tell her to put an ad in the paper, posters up around the neighborhood, pet stores, vets offices and to call the shelters around her. You can also put a lost ad up on http://www.birdhotline.com/
(this site was a big help when I lost my tiel a few people got ahold of me)
Tell her not to give up hope! You would be suprised how many are found. I would keep a light on outside at night and put his cage outside opened somewhere where he might be able to see it.