This unlikely diode reminds me of stories I've heard about people hearing faint radio reception from strange objects such as household plumbing or (IIRC) even their own teeth!
Of course a purpose-built radio receiver includes niceties such as tuned circuits. Parasitic receivers lack these, and consequently receive all stations at once (with the strongest signals most loudly audible). The heart of the circuit is the diode, which serves to demodulate the AM signal. This fellow's "wet diodes" give us some insight into how semiconductors can be created by accident.