In Manchester City's 2-0 victory at the KC Stadium last Saturday, Boyd went down in the penalty area after Joe Hart charged out to claim the ball.
Hart was clearly incensed by what was adjudged to be a dive, with a confrontation breaking out between the pair.
At the time of the incident, referee Lee Mason issued a yellow card to City 'keeper Hart, for getting in the face of Boyd.
But television footage in the aftermath of the incident appears to show the former Peterborough United star spitting at Hart, which then sparked the confrontation between the two players.
Speaking post-match, the Scottish international stated his belief that the England international should have been shown a red card, but made no reference to his own involvement in the incident.
"He didn't nut me but he's put his head in, so he should have got sent off really."
It was confirmed on Wednesday afternoon that Hull City would fight the charge, with Hull boss Steve Bruce vehemently denying that Boyd would spit at an opponent.
On Thursday morning, their case had been thrown out by The FA and the original ban upheld.
"George Boyd would not do that, not a chance -- not deliberately, anyway," Bruce said.
"He is as honest as they come."
Now that Boyd's appeal has been unsuccessful, he is set to face a three-game ban that will see him miss vital clashes with West Bromwich Albion, West Ham United and Stoke City.