I made the mistake of letting a friend who was trying to learn PPC have a look at my account. Later a comment made me wonder if he had a copy. Is it possible to detect if someone has used the Editor to download a copy of my adwords campaign? Of course google could tell me via logs but I am sure they won't do that. Is there anyway I can detect this?
You mean you gave someone your login info? You can run the change history report and see every change in your account. It doesn't however, as far as I know, show when a download has occurred. In fact, it shows only changes, it does not show when someone simply logs in. Google can tell you about log ins and even which IP it came from.
I doubt Google will share any log data, especially since you gave away the login, so it wouldn't have been illegal for him to download it. Just learn from it, change the login(s).