I can't help but think that memory loss should be one of those things that is discussed more widely when convincing the inexperienced to deter from deep air dives ...
I have a story... we had four divers on a 55m deco dive to Sweetlips 'Cave' (more like a swimthrough really, you're never lightlocked per se). At the entrance, my buddy gave his small torch to another diver to go through. On the other side, he asked for the torch back and got a :shrug: After the dive, said diver insisted that they had not been given a torch
The torch was recovered on a later dive to the same site, lying in the sand outside the entrance
I've also known divers to go 'unresponsive' at 50-60m on air, to the extent that they had to be escorted up from depth. They subsequently had little or no recollection of anything between some time during the descent and somewhere around the 21m deco stop during ascent, or thereabouts, when they 'woke up' again
Obviously this could be potentially a very dangerous situation, and there are plenty of stories about people not levelling out at the target depth who just kept descending - often without a happy ending