I hit a pothole hard enough a couple months ago that one of my water bottles got knocked clean off the bike and I didn't notice it was missing until a moment later when I felt more breeze than usual on my legs. Anyhow, this pothole managed to give my back wheel a rather large flat spot, but the crazy thing was I didn't notice it until a week and a half later when I noticed the brake pad rubbing, and I was riding the whole time. So yeah.. check your wheels and keep checking them - problems don't always show up right away.