I used to have title "Sexy" and "Superstar" but I can't find them on the title list anymore. I also tried with command /title 126 but nothing happened. I'm sure I had those titles and I checked my list million times. They are gone! How can I get them back?

Maybe you can try to clear your cache?
Or restart a million of times until you see them.

I lost my <Temptress> title as well a while ago. I'm not sure of any other titles I lost.