I'm not sure but I don't think you do find him again, he gives you a quest to investigate the seven suns and then after you've proven yourself he sends you to meet with the duke. Check your journal and see what the latest quest you have is.
That command only creates the Scar that first meets you at the bridge.
However, after he walks away, Scar reappeared for half a second in the Flaming Fist building, which was just enough time to claim the reward. I'll probably be able to get the other quests this way too.
No. In the Flaming Fist HQ in the SW area of Baldur's Gate (the prison, where the Duke is), he was inside. I talked to him. He said that he needed to talk to me about the Iron Throne and said he would be inside the Flaming Fist "Barracks", and walked off and vanished.
I don't recall any barracks or Scar ever even mentioning barracks. You have done the Seven Suns quest (and maybe the optional sewer investigation quest) I assume? After doing those, he will take you to the second floor automatically to meet the Duke who will give you the quest to investigate the Iron Throne.
Gah, it even says in my journal that he's in the barracks.
And now some person on the street came up to me and told me that Scar wanted to meet me in the Flaming Fist "Barracks" in the SW corner of the city. Ugh, the HQ must ALSO be the barracks.
Which means he's inexorably bugged. Fortunately the console hax will spawn him, and then he chats you up like he did when he first met you on the bridge. And then after he walks off from that he appears for like 1/3 of a second and vanishes again! But if you can pause the game and talk to him in that 1/3 of a second you can complete your quests....