With all the cynicism abounding here, and my heart goes out to you...
I am VERY blessed. I took on three stepsons years ago. We now also have two of our own. NO difference anywhere - They/WE are ALL family. I am VERY BLESSED!
My oldest stepson, 25, is getting married to a wonderful girl in Sept. He is estranged from his biological father. He told his mother, anyone can be a bio father, but Steve (me) is my Dad. That makes it ALL worthwhile for me.
His younger brothers (other 2 stepsons) basically feel the same. This means a lot to me. And, all 5 boys are thick as thieves.
Unfortunately, your generosity bit you. But it doesn't always turn out this way. You obviously have a lot invested in your adopted daughter (and I do NOT mean monetarily), and I hope you find out where she is and that she is doing ok. It is obviously weighing you. Just know that you did all you could do. Take care.