How can I tell if "find my iPhone" has been used
No, simply using Find My iPhone to find the location of the phone doesn't record the action anywhere.

Turning off location services will mean that Find My iPhone won't be able to obtain the location, unless Lost Mode is activated.


  In iOS 7, if you turn off Location Services and use Find My iPhone Lost Mode, Location Services will be re-enabled on the device as long as the device is in Lost Mode.


Source: http://support.apple.com/kb/HT5594