Hidden folders/files in XCode4

I dragged in a folder containing a few files and copied them into the Classes folder. I tried to use the files, XCode picked up the header when I added the #import line but said file didn't exist on compile. So I deleted the files, not just Remove References, then when I try and 开发者_StackOverflow中文版add the files again, it says they already exist!

Where are they? and how can I delete them properly and or start using them again?

Turns out the empty folder was still in the actual file structure in Finder.