This may sound crazy to most of you but when Scratch was talking to "Angel" as he lay he was very Scittish, not at all like the Angel we all know. "Angel" also apparently had his face entirely ruined so there is no way for them to know it was Angel. Now.. there was another guy ontop of the Tower, forgot his name but he got knocked out I believe, I think that he might have stolen Angel's ring or potentially was part of that "family", that's a big stretch though.
The only proof Scratch had that it was Angel, was the Ring and it's made clear. Shaun, CJ's Shaun from the other Tower also was part of the other Town that Michael and Pegs went to, those are my guesses though.