"Locate" is not an "app", per se -- it is actually a function called "Find my iPhone" and is built-into the latest firmware running all Apple iOS devices (Pad, Phone, Touch) which is accessible through iCloud.
And to answer a question, it also includes "disable" and "wipe" functions at no extra cost.
If your iOS device does not have this function, you may need to update your firmware...
That is not actually correct. 'Find My iPhone' is an app that you download from the app store. Go to the app store, search on 'find', and it will likely be the top one on the list.
Imagine a thief's surprise when he pulls up to the clubhouse in my Saturn, lol.
But seriously, years ago it might have been reasonable, but these days, with the sheer number of Apple devices out there, it would be a logistical nightmare for them. Years ago there might have been 10 million ipods out there, today there are probably 500 million of them.