I forgot mine for the first time I can recall just a few weeks ago. We were 20 miles into the ride and my wife finally asks me where my helmet was. I had stopped for a "natural" break and she was afraid I'd taken it off then (Hey, don't you call me a d!ckhead ) but no it was back in the car. I wouldn't have realized until the end of the ride if she hadn't spoken up. Others in our group either didn't notice or just thought I was being rebellious.

Like many of us who rode in the 80s (or before ) I rode 1000s of purposely helmet-less miles but this is the only time I can recall just forgetting to put it on.