I just read on the NOLS blog that the beacon was dented and didn't work at first.

http://nols.blogs.com/nols_news/2011/07/...-in-alaska.html

"but all organizations need to assess every incident and think what they would do differently, NOLS needs to rethink the lack of a wilderness medicine trained and certified pesonnel with the kids, that the GPS beacon was dented and did not immediately work, that the training of how to handle bears did not last in the panic of the moment, etc., etc."