I learned years ago, just about the time I realized I was neither immortal nor indestructible, to carry a few things with me at all times. By that I mean in our vehicles, on our bikes, in the boats when we had them, at work, in the backpacks and etc. We didn't load ourselves down, but ear plugs, important maintenance medications, a little bug bite cream, toilet paper, spare glasses and a few others things didn't make either a large or a heavy package. It all to this day still fits in a Spec-Ops bag that's maybe 8x8x2 inches.
I do this to this day and I've encourage my kids to do the same. People DO forget to take stuff along, the unexpected does happen and a little up front planning can go a long way toward saving an outing. Other than that, time to play MacGyver and do the best with what you have ... cigarette butts notwithstanding.