On my recent cruise to Alaska, I realized I had forgotten to pack my NP passport book. We visited Mendenhall Glacier, a federal recreation area which sits in the Tongass National Forest. As I listened to a ranger talk at the visitor's center, I was very disappointed not to be able to collect my first stamp.
A few days later, we visited Denali National Park, and again I was lamenting not having my passport book with me. So I went into the visitor's center to buy a new one. They told me they were out of books, but that I could get a stamp at the main desk and put it in my book. I walked over to find people stamping small pieces of paper, so I did the same. As I pushed the stamp down on that scrap, I said to the ranger, "I forgot my passport book," and she replied, "You're the only one who ever has." (wink!)
When I got home, I carefully cut around the stamp and glued it into the Pacific Northwest & Alaska Region page. My first stamp in my book, and it's from the king of all National Parks, magnificent Denali!