If you went to fabrication output, and selected Gerber files, filled out all the appropriate boxes, and checked tha appropriate boxes, you DID generate Gerber files.
If you are using DXP2004(SP1 or later), the files will be found in the project directory for your board in a sub directory called "Project Outputs for xxxxx", where xxxxx is the name of your project. If you are using an earlier version of DXP, the files will be in your documents directory - you'll have to hunt for them.
The .CAM file you think you see is just the default file extension that would be saved from CAMTASTIC. You apparently have CAMTASTIC set up to open automatically when you generate gerbers. This display is just for you to check - it doesn't change the gerber files you have in the directory I mentioned above.
Use your operating system browser, and you'll find that all the necessary files are there on your hard drive.
All of this is discussed under Help>Contents>PCB Fabrication and Assembly.