The Persistence of Memory

I was practicing memory today before I was fully awake (I'm turning into a very late riser just recently - with not working, I seem to be shifting into a 25-hour day pattern and not getting tired until later and later at night), and getting on quite well - slightly slower than my best times in memorising, but recall much closer to 100% than usual without needing to think about it. After finishing with numbers and binary, I had a go at some speed cards, and only as I got to the end of the pack did I get a slight sense of deja vu. The last six cards were two fives, two sevens and two tens, and I thought to myself "didn't I memorise another pack a while ago that ended like that?"

Thinking back over the past minute or so, I suddenly realised that I'd picked up the pack of cards from the pile on the right-hand corner of my desk, where I keep the cards I've used in previous memorising sessions but haven't got round to shuffling yet, rather than the pile on the left of shuffled and ready-to-memorise packs. How can I remember the sequence of a pack of cards without too much effort, but forget an instinctive thing like picking up the pack from the left side (which is how I've ALWAYS kept my cards)?

Makes me wonder if I've done that before without even noticing it. As a side-effect of learning to memorise cards, I've developed the ability to instantly forget them after I don't need to recall them any more (so that I can reuse the mental journey they were on), and it was only that distinctive run of cards right at the end that rang a bell. Perhaps I'm actually just a big giant fraud, and whenever I think I've memorised a pack of cards in training, it was actually just the same pack over and over again.