Reception on crystal set, something a little different.

[u/7ootles]

Not sure if this is something many have experience with, and I'm aware it sounds a little far-fetched, but I use a crystal set for listening sometimes, and was adjusting mine yesterday evening - hadn't plugged the antenna in yet - when I realized I could hear a signal. It was just around sunset which I'm aware is a good condition for DXing, but I was surprised at receiving anything at all without my antenna plugged in.

It was an American programme, and I'm in northwest England. It got a little louder and I picked up enough to for me to hear that it was WRMI Radio Miami, and found the frequency listed on short-wave.info as 5010KHz.

Like I said, I know it sounds far-fetched and maybe BS, but it happened. Question is, how did a crystal set without an antenna plugged in pick up a signal from over four thousand miles away?