I had no problem searching Çroaker and Wìdowmaker on Battlenet.

Is the character higher than level 10? The only character I couldn't find of mine that uses alt codes was Lõrdãpophis, which is a level 4. I also checked one of my husband's old toons, Winterscream, a level 5. Several Winterscreams show up, the lowest of which is level 11.

However, as Peli said, they will still show up on the roster if you search by guild.