You can use a gps or a app on a IPhone. I used to use a handheld Etrex until the app on my sons IPhone was so much easier to use. If you don't have those just google the long and lat and it will show you to the coordinates of the item.
What Iphone App does your son have? just curious as I'm not sure whether the standard mapping sows the GPS coordinates. I have an old Etrex that my brother gave me also and without mapping it's very limited in it's uses.
If it isn't found, my next day off will be looking for it...of course my next day off is the 13th, so I'm sure someone will have snagged it by then.
Yup found it earlier today. It was a fun long hike, around 6 miles round trip from where we parked. Had a blast and got to spend some time outdoors.