spark plug mystery

[tirebird]

My engine must be in the twilight zone. Yesterday, I was starting to adjust the valves on the LS6 when I discovered something I've never encountered before. You know the old rule, do something long enough and you'll see something you've never seen before. This falls into that category. Before pulling off the passenger side valve cover, I decided to disconnect the spark plug wires from the passenger side at the distributor. I did, and when I carefully pulled the wires aside, one of the spark plug wires(#4) also fell off it's spark plug. But wait, it gets better. The boot inside the wire had the screw-on sparkplug tip. That means the tip unscrewed from the spark plug while attached to the spark plug wire! How does that happen? The spark plug doesn't rotate and neither does the wire boot. So, the tip had to rotate while attached to the boot. The spark plugs are about a year old(3k miles) and no, I didn't notice any engine misses while driving so I think the boot(Taylor SpiroPro) was still attached to the spark plug insulator. I can't explain it.