Thanks for the correction. I always thought it was Leary, and never checked IMDB for confirmation.
As for the question at hand. I’ve tried to think about this from any angle that would not include Erie in the explanation of the con. I can’t.
If the runner who was eventually killed was questioned before his demise, he would have explained how he came to get involved with Hooker and Luther. That always includes the mugger (i.e. Erie).
Even if Erie wasn’t a Coleman regular, I would think a local tipster would be able to finger Erie quite easily. Even if Erie wasn’t readily identifiable, the third man would have to be exposed as a role in the con. Finding that out may take more time, but Lonnigan had no problem taking the time. “We must discourage this sort of thing. Ya folla?”
Not a major plot hole, but it still bugs me. Especially since Snyder found out about it, stopped Hooker and Erie on the street, and focused his attention on Hooker. The thing about this scene that bugged me was that Erie didn’t show any concern that he was also fingered and would be shaken down, but Snyder implies that he knows he was a part of it with his parting comment, "Relax,“Erie” (I always thought he said “Jerry” here, but it looks like I was wrong), “I’ll bill ya.”