Memento Memories

How would you explain it?
My long lost fishing buddy Patrick, who lives in Australia now, was visiting here in Montana last week. We wanted to float the Yellowstone during hopper season but the river was blown out: chocolate brown after several days of strong evening thunder storms.
So we hiked in to the lower end of a well-known cutthroat creek in the park and worked out way back upstream. We absolutely wacked'em. We must have nicked 30-35 fish apiece. I did find, however, that each fish would rise up and inspect my foam/deerhair hopper only once. They'd either bite or reject it, and then that was it. So I moved fast, drifting my hopper over ever good looking riffle drop and bank-side eddy and then moved on upstream, without spending much time at any given spot.
And then I suddenly realized I was fishing out in front of my buddy Patrick, who I was supposed to be entertaining. I strode quickly back downstream with my hat in my hand and apologized to Patrick for not hop-Scotching pools with him. Patrick laughed. "You always do that," he said. And then he added "but it doesn't seem to matter. I've been wacking a dozen fish at every pool too. But they only look once," he added. "Any more that two casts at any given spot is a waste of time!"
Patrick was fishing a small, hard-to-see black caddis pattern. This was really perplexing. They'd only look once at my hopper, but they'd still come up to look at Patrick's black caddis. It made me wonder if some else could have come up behind the two of us and wacked'em with a Pale Morning Dun, or a wet fly, or whatever.
When we finally turned around, about 2-3 miles upstream from where we'd parked the car, we agreed to hop-scotch back downstream, fishing over the same holes we'd banged on the way up.
We fished quickly but carefully. But we rolled only 2-3 more fish on the way back downstream--between the two of us. Those same fish still remembered the hopper and they also remembered (or at least wouldn't bite) the black caddis.
What kind of Memento like memory is this? I have a strong suspicion we could have returned the following day, and repeated the same scenario. How would you explain it?