I always get a chuckle when this happens. I've been guilty of bringing back a couple of old threads in my day.
It usually happens when I'm really tired and winding down before bed. As I get sleepy, my ability to pay attention becomes questionable at best. While searching for parts and jumping between pages, I've accidentally clicked on one of the "Similar Threads" near the bottom, thinking I was back at the front of the forum. I usually don't realize what I've done until the next morning when I'm wide awake. Getting too old...