Can you describe it better, or supply pic of area. I have a cylinder bolt spring and detent from a 638 if we are talking about the same thing? (I don't think we are).
I made the same kind of mistake, but I'm much better now since they changed my medication!
FYI: S&W did send me those parts no problem when I called them. I know sometimes it is an issue, gunsmith wise, but If you talk to them like you know what you are doing, they will almost always send the parts gratis.
Chuck