The Spanish official awarded the visitors a late penalty in the Catalan derby, which Lionel Messi dispatched to hand the champions all three points.
However, Lopez, who was adjudged to have handled inside his own penalty box, has criticised Gomez's involvement.
"Clos Gomez was the winner," Lopez told reporters. "The penalty was just bad luck. The ball bounced up and hit my hand. You can see how my lip is [from the tangle with Javier Mascherano] but he didn't call for a penalty.
"We can't look at what's in the past. We made things very uncomfortable for them. We never lost face and had two or three very clear chances."
Lopez was forced to finish the match between the sticks after goalkeeper Kiko Casilla was sent off in the latter stages.