Are you guys discussing that maybe she was so high that she doesn't remember what happened?
Being an old "flower child" and knowing many people who used drugs heavily back in the day, I have never heard of someone who "forgot" because they were on drugs. I have heard of people who black out on alcohol, but aren't they usually long time alcoholics? I'm not sure on that one.
I do not believe she was blacked out. The drugs that we have reason to believe she was using do not result in black outs. By the term "black out", I mean, having been awake but with no memory.
I think it is very possible she could have been passed out so cold that somebody could have come in the bedroom and snatched Haleigh and she would not have woken up. If she had been on a 3 day binge, she needed sleep. The reason you wouldn't want somebody watching kids who had been on a three day binge is they wouldn't be as alert and they might not wake up even if smoke alarms went off.