Just to add to what others have said:

The beacon was only picked up by a satellite. Why couldn't the rescuers triangulate on the beacon? Well, in order for ground or air searchers to do so, they'd have to be close enough to pick up the signal. So it's a "catch-22" situation - in order to find the plane, they have to know where it is. (At least approximately.) Triangulation by ground or air rescuers allows them to pinpoint the location more accurately when the general location is known. I doubt the difficulty had anything to do with lack of the proper equipment, as someone suggested (though that poster probably knows more about it than I do).

Given the fact that only one satellite was able to receive the signal, my guess is that they went down in a deep, narrow valley, in which case the searchers likely wouldn't have been able to pick up the signal until they were practically on top of the downed aircraft.

I understand the searchers did, in fact, locate the downed aircraft within a day and rescued 4 of the 7 occupants.