lost cockatiel

Any suggestions on finding a lost cockatiel?? Posted on Parrot911, ParrotAlert, numerous FB sites, Craigslist, have a mating call on phone, posted fliers at vets and different neighborhoods around town. After all this work, there's not even a sighting of him even though there have been several sighting of other cockatiels. We fear that someone has him and will not post anything about a lost bird.