You received a lead, but realized that the driver doesn’t really what it takes to work for your company at this time. You moved on and driver has moved on as well. In a year or two that driver may be in the market for a new position again. Will he remember you? Most likely not unless you stayed in communication with him/her. Easiest way to do so- EMAIL! Sending regular and informative messages will not only ensure that your are always on their mind, but also that you are an industry leader and an expert.