NDEs are rare to begin with, though becoming more common with modern resuscitation methods. But if a person is full of hospital drugs at the time, they are unlikely to have a clear memory of anything. Same with drug-induced comas - the people that come out of that don't seem to have any memory. I read once that a person who'd had an NDE and recalled it once back in his body, was of the opinion that if the person didn't think about the memory very quickly after recovering, they would lose it completely - just as you do in the morning when you awaken from sleep, have a fleeting moment when you know you'd been dreaming about something, but unless you can recall a bit about that dream, the whole thing eludes you. But if you can think of a scene, or an item, or person, or words in the dream, usually the whole thing comes flooding back to mind.
Perhaps if scientists want to conduct experiments to verify this, they need to get all medical staff involved to ask the recovered patient if they experienced anything unusual.
Well, when I was a toddler I was concussed, breaking my collar-bone, and was taken to hospital. I was too young to remember anything after hitting the ground (though I have a clear memory of the events leading up to the fall). But one of my earliest memories was of looking down on planet earth from being way out in the universe. The blackness of the universe contrasted sharply with the colour of earth and I was a great distance away from it. Linking me was a thin silvery thread or cord that curved from my left side down, down, down, back to earth. That dream-like snap-shot memory was one of my earliest. It didn't make any sense. Until I was much older.
Despite parental teaching that there is nothing after death - no soul, no awareness - I noticed what Ecclesiastes chapter 12 says about the silver cord being broken at death, and our spirits returning to God, who gave them. I now realise that I was on my way back to God - my spirit had left my toddler body in the hospital. But it clearly wasn't my time, so I was brought back. Don't forget - this was when I was no more than a toddler - in the early 1950s, decades before out-of-body experiences were of popular interest, and eight years before satellites began orbiting earth, sending back photos in November 1959, before we even had a black and white TV in our home. How could a toddler know she lived on a planet that looked like that, from heaven? And where in all creation would she 'know' about that silver cord? I had no preconceptions, and no religious teaching at that very early stage of my life. Links below for more on this subject.