They should be FPSC under a folder called purchased, you should be able to open the editor, add new entity(or whatever you purchased) and find what you bought under purchased.
What might've happened is that when you downloaded them they weren't set to download to your FPSC folder, that happened to me and I couldn't find my stuff for awhile.
Now this is completely from memory so I might be wrong but inside the store on the bottom toolbar where it displays your login details and points it should have a button that says "download options" or "options" just look across the whole thing and you should find it. When pressed this button takes you to a window which gives you 2 options, download to FPSC or download to a specified file. Check download to FPSC and redownload whatever it is you can't find and it should be there for you.
Hope this helped!
dark peanut
Look for me on CoD4 online for PC. My username's Arbiquator (strange I know but it's the first thing that came to mind)
