Whenever I hear about stuff like this, I wonder: Is there anything the failure modes of the human brain allow us to deduce about the software architecture? Maybe memories are stored in some partitioned database, and one of the partitions is always stuff relating to "my identity", and somehow this partition can get unlinked and temporarily re-linked to a blank one, which is discarded after a few hours. Hmm, maybe this…
This is why a lot of cognitive psychologists study abnormal psychology. It's when things break that you can find out what's going on. I do think being able to blank things out (including times of immense pain) is a feature that increases survival rather than a bug. If you are excessively afraid, your ability to pass on your genes goes down.
Please correct me if I'm wrong, early part of Medical academics is all about studying how a healthy body body works. So that when they start studying the diseases they can learn to distinguish between a disease and a expected behaviour.
So to know if something is an abnormal psychology, you need to first know what is normal.