Diesel engine running while fueling causing a leak?

I left the engine running the other day when I put diesel in. A guy at the station said I had something leaking. The leak is from the area where I put the nozzle in to the tank. The leak to me appeared to be from not the fuel line but the bigger line which I assume is the circulation line. I drove home about 1 mile and it was still dripping. There is a jubilee clip around a pipe connected to a hose which may be loose but was the leak caused by me having the engine running while fueling? I have not seen the leak on the drive way when the car is off so I assume if it is a leak it is from the circulation system which would only be running when the car is. The car is a 59 plate ford focus 1.6 tdi