B737-800
Maintenance Airframe; Maintenance Powerplant
Distraction; Other / Unknown
Aircraft Equipment Problem Critical
Flight Crew Returned To Gate; General Maintenance Action
Procedure; Human Factors; Aircraft
Aircraft gate return after vertical stabilizer pitot static cover was spotted from another aircraft at airport. A walk around check was accomplished [early in the morning] during heavy fog and limited visibility condition after the aircraft was wet washed during the early morning hours pitot cover flag was facing out the grey dark color side that made it harder to spot installation on aircraft.
Line Technician reported a B737 returned to the gate due to a pitot static cover not being removed prior to departure.