In their user profile somewhere.
Open a command prompt, then type:
cd \
dir cameras.cfg /s
This may take some time, but this will scan your entire C: drive for any files called “cameras.cfg”. Or rather your friend should run this.
The files they are looking for will likely have “LocalCache” in the path somewhere. Note the above will only work if they have created at least one custom camera view for any plane, otherwise it won’t have anything to find. The other thing they could search for, and actually this would be better, is the “state.cfg” file, as that should always be there.
So:
dir state.cfg /s