I cannot beat Confidence man. Scarlett, right after the fight will teleport never to be seen again. I've done the fight so many times now i can end it in 2 swings trying to figure out a way to keep her from teleporting. I waited a total of an in-game month waiting to see if maybe she'd show up. Nope. I'm not sure what is going on but it is highly annoying and breaks this entire quest and removes an entire character from the game, seemingly permanently.

Have you looked for her around the city? I think when I spoke to her, she was walking around the Diamond City "announcement" area, where you paint the wall. I think you actually have to talk to her outside of the bar, because of the future stages of the quest, if I'm not remembering completely wrong.

edit: Mh, might be wrong here, as its listed as a known bug on the wiki page :/

I walked around and couldnt find her but I'll try again. I did once wait for her to walk out of the bar and I didn't look for her. I'll try that again. When you did it, did you wait for Valim to walk to the corner of the back room? She seems to make a bee line for the exit when he starts to walk over but if you initiate a conversation with him she teleports away.

Follow up! She was in the announcement area. They fail to let you know that and seemingly failed to give me quest markers.