atma weapon

i didnt get the atma weapon in the world of balance, in the sealed cave, and now im in the world of ruin, can i still get the atma weapon?

No.

Well, you can steal one in the last battle, but you can only use it for that battle.

I might be mistaken, but can't you steal one from the second Atma weapon too?

Yes I do believe you can in fact steal one from the second atma weapon, although it is still relatively useless at that point in the game.