A few users have posted before about using cheap GPS dog trackers that use cell phone sim cards. I have not heard the results of these tests but would be interested in hearing their results.
All my flyaways have always been into the ground or a tree line and thankfully has only happened twice.
HPR - High Power Rocketry and many others have been using the following items with great success for several years now.....very reliable and very long range. http://www.bigredbee.com/brb900.htm
site looks hokey but don't let that fool you.
Thanks Peter, I discovered the rocketeers and falconry use of radio tracking shortly after I posted the above. Seems like they are way ahead of us for tracking. Found a supplier of radio trackers- ComSpec out of southern Cali.