That's why several may have been useful. Seems daft to have no method of letting the surface know your approx position, on an ongoing basis. Anyway, it seems clear that they have no means of communicating anything at all, so it all looks incredibly bleak.
I would have assumed that there would have been some form of emergency beacon/transmitter/similar, should this kind of situation arise? Not saying a rescue attempt would be possible, but at least giving their location.