EMB ERJ 145 ER/LR
Other / Unknown
Aircraft Equipment Problem Critical
Flight Crew Returned To Departure Airport; General Maintenance Action
Human Factors
We departed and around 10;000 feet MSL the Flight Attendant reported that the left fuel cap was missing.  The crew decided to return to the airport.  Upon landing the crew verified that the fuel cap was indeed missing.  The airport Operations found the fuel cap about 2;000 feet down the departure end of the runway.  On-field Maintenance inspected the plane and found it to be airworthy.  The crew then departed without further incident.
EMB145 First Officer is informed by the Flight Attendant; while climbing through 10;000 feet; that the left fuel cap is missing.  Flight returns to departure airport where the cap is found down the runway.