Serendipidity and Writing

I'm in the middle of reading the page proofs for the UK Puffin edition of Nim's Island. When I came to the description of Nim lighting a fire:

"She unscrewed the lens from her spyglass. She pointed it so that the sun shone a bright beam on her kindling. A brown patch grew and glowed - and a small flame sparkled on the dry palm fronds..."

I suddenly remembered that I'd written that after visiting a friend who'd just had a fire in her living room. Her reading glasses had been lying on the newspaper on the coffee table - in just the right way that the sun hit them and heated up the newspaper till it burst into flames.

Would I have thought of Nim making fire this way if my friend hadn't told me of her scare? Maybe; maybe not. That's why I love writing - because I never know what I'm going to discover till it happens.

Right now (at least once I've finished reading these proofs) I need to discover whether the pony tail I saw the other day will find a place in the current work in progress. I think it belongs there - but I won't know for sure till I write it.