I biked to the DeYoung museum in SF. While locking up my bike I stepped back onto my bike helmet and my back went out. I could barely move, let alone bike anywhere. I ended up laying on the grass for a while hoping the pain would go away but when it didn't I started contemplating getting home. I couldn't take a cab since my bike wouldn't fit. I wasn't going to just leave my bike. I was finally able to get a hold of a friend who came and got me. He put my bike in his trunk and got me home. I was very thankful for my cell phone.