This is tough question to answer, but I will do my best. They all have a similar meaning, but they can imply different things. "I had lost her." This is personal. The person speaking has lost the girl. All the others are Impersonal. "She was lost." lost can imply that she doesn't know how to get back. "She was missing." missing here can suggest that no one knew where to find her, but she may not be lost. This also implies she has been found, and is no longer missing. "She went missing." This can imply a longer time has passed. This could refer to the time it happened. As in She went missing a week ago. "She was gone." This can imply she will not be coming back, but can also imply she just walked away and is not lost or missing. "She had gone." This implies that she chose to leave. Hope that helps.