The bike was stolen from a front mounted bike rack on a MUNI bus in San Francisco. Aside from using the spring loaded mechanism to keep it in place, there is no way to secure a bike from theft otherwise.
Protect your bike – get a security protection label!
Apply the protection label to your bicycle and instantly reduce the risk of theft by up to 50%! Moreover, if the bike is stolen, you increase the chance of its safe recovery by up to 70%.