To return back to the topic, i don’t think this person will forget his past life, or at worst temporary. I had a bad experience with drugs, that seemed like to last decades (even a century at the moment…) and, even if I forgot almost everything I experienced in life at the moment (I only remembered basics like mathematical add and substract but not much more…), when I woke up I quickly recovered all my memories. But yes, I think this person would be depressed, because I was inversely very very happy to come back from this bad journey.
Anyway the great advantage of LD’s are that you can awake whenever you want, so this scenary should never happen.