Download app on someone else's device? If I sign into someone's ipod to download something, using my ID &amp; password and forget to logout, will I be able to locate the device using Find My iphone?
Not unless your Apple ID has been logged in for use with Find My iPhone. Chances are this hasn't happened, since the iPod can only be associated with a single Apple ID  at a time for the purposes of device registration and Find my iPhone.