I’m glad someone else has the same story because when we tell stories about our standard poodle who could dive 7-10 ft down and return with the same rock we are sometimes not believed. Used to win bets at the beach, “throw as far as you can, he’ll bring you the same rock” was the bet.
Your post reminded me that my husband and I watched a man playing fetch with his dog along the shore east of Brighton, UK. He claimed his dog would bring back the same rock.
We never made bets, but my sister’s Golden Retriever would do the same thing - amazing. I’m guessing it was the smell of our hands on the rock. I had her dog out on the boat with me fishing once. After about a half a day and stopping at perhaps 6 places, I finally figured out that she was calm in places where I didn’t catch fish, and would bark a little and get excited where I would catch fish! So that afternoon I just went slow around the shore and stopped when she got exited. I figure the same thing - she could smell them.