W/o intoxication from any substance, but just walking down the hallway (I did today 3 times in my music building), u are so obsessed by a thought you literally black-out, and realize you walked to the wrong place?
I've had experiences not dissimilar to that while playing music from time to time. I've nicknamed it "the zone", though I suspect other people call it that, too.
I once played a version of Matt Dennis' "Angel Eyes" for a talent show in middle school. I remember sitting at the bench and adjusting it, I remember playing the introduction, and then I remember cheering. It's one of my favorite memories. I used to have a cassette recording of the show, and I did a really decent job. It was bizarre.