"The CIA used a futuristic new tool called “Ghost Murmur” to find and rescue the second American airman who was shot down in southern Iran, The Post has learned. The secret technology uses long-range quantum magnetometry to find the electromagnetic signal of a human heartbeat"
Note, I agree that it was probably some novel beacon technology. Just answering your question about why people are debating whether it was a device that could detect a human heartbeat from long range.
https://www.seattletimes.com/nation-world/nation-politics/in...
Not that I believe any of those words are true beyond the code name. The incident is exactly the kind of thing you'd want to create false rumors about
The transmission itself would need to be stealthy or separated (by distance and/or time) from the pilot. For example, the pilot might leave a transmitter to send a message "moving south, will hide on X hill" hours after the pilot leaves, or even toss a transmitter into a river. But most likely just very spread-spectrum/CDMA to make it indistinguishable from noise.