What a scary thing to happen to you. I understand why it's seared into you memories. Spirits are so strange in their intentions of wanting us to see them and then scaring the heck out of us when we finally 'look'.
Perhaps it needed an extra jolt of power and chose you to get it from. I've read that our fear gives some spirits power.

Thanks so much for sharing your story. I agree with your theory on natural energy flows in the earth.