How can I fix the Electrolux Concept 2 upright vacuum cleaner?

The mechanism that locks the upright body to the base containing the motor. wheels and rotary brush has failed. This mechanism is normally released by depressing a foot operated control that allows the body to lay flat parallel to the floor. The problem seems to be related to a small piece of spring steel that I found on the floor when the problem occured, but I cannot find a place for it. Does anyone have an exploded view diagram or experiece solving the same problem?