In doubt, need explicit answer
 

I created joined trill as my first character, if I delete it and make new trill will is still get joined trill as trait, or it is lost?

Can someone answer me please?

You should have it again as it's tied to your account, not your character.

How did you create a Joined Trill? I thought they only unlock with your retails key.

I guess he created a Trill and thought it was a joined trill. Trills officially are unavailable till the retail key comes in, which will be in 2 days at least.

Or perhaps he got the retail key (could be working in a game store). You'll always be able to make one. Well, as long as the game exists.