If you've ever played football, you'll know that's not particularly the case. It sounds like a "gotcha", but the reality is he probably said to his teammates "yeah I think it probably was out" or something like this, but it doesn't mean anything.
When I was playing football a few years ago, we conceded a goal where our keeper misjudged his position and the ball went over the line, on a corner - 20 players (all minus the 2 keepers) saw that ball cross the line. The ref saw it cross the line. People in the town next door could probably see it cross the line. To this day, our keeper still maintains that it didn't cross the line. I don't think it was embarrassment at conceding a goal (he was shit anyway and was usually quite willing to make fun at himself for his own mistakes), and it the relentlessness with which he maintained his stance showed he truly believed it. He was wrong, he was theoretically the best player to judge it, but he was absolutely wrong.