Inspiration - The magic moment

There are times when writing you are drawn from anything around you and into the story completely. This afternoon I had one of those rare moments while writing a scene between two villains. When my son appeared at my study door and spoke, for a moment I wondered who he was and where I was. I had been so deep into the characters and the development between them the entire outer world was gone. These moments don't happen often but when they do one has to go with the flow. When the moment is broken it's hard to get the rhythm back. I once wrote the rough draft of a novel working 72 hours straight. When I finished and the moment dissolved I looked at what I had written. Was it awful, no. Was it wonderful, in spots. But that long moment allowed me to plot an entire book that later I was able to smooth out. I don't want any of the magic moments to last that long but I do appreciate them when they come. Have any of you experienced these moments when the house could burn down around you and you would be so lost in the story that the sound of the fire engines would startle you into the present?