The recorder itself does not have to survive, just the data capsule. That they have not found it is not difficult, it probably is buried in the ground, and you will have to basically go looking for it with a metal detector to get it, and pick up a half million little bits of mangled plane as well.
The pinger is located on the recorder frame, and the design there is it will activate in water, though it may not be attached to the recorder itself and have torn off. It too will survive the impact, but is not designed to survive the cooking, seeing as it operates with water so if it burns on ground it is not needed. It tells you where the back end is so you can search for the drowned plane.
I have seen plane crashes where large items tore out of the frames they were in, and went through very substantial aluminium castings after making a somewhat mangled box shaped hole in it.