That is called an awakening. It comes when your ego stops telling you what you are. This happens spontaneously to some people and tends to last only a little while. It can also be induced or guided so that it continues longer in a controlled fashion.
Your experience of "poof it was gone and I was only left..." is your ego reassurting itself. At this point, the "I am" of your mind restricted your understanding and limited your experience. That's very dissapointing and leaves you feeling frustrated.
By trying to remember, your experience was censored by your mind. You couldn't remember because the human mind is not built to store that amount of information.
Be very careful. Learn meditation a.s.a.p. because you will need it!
Take small steps to make your ego flexible. By flexible, I mean there are times when you say "I am" but it means one thing and at other times "I am" means something more.
You had a moment of "I am" that was bigger than normal. When the ego snapped back, it described it as EVERYTHING. Unfortunately, that's not very usefull to you is it. :)
This experience has WAY too many names.
Strengthen your body and open up your mind because your soul has spoken in a big way.