The Reds second row was alleged to have stamped or trampled on Lions lock Alun Wyn Jones in the third minute of the tourists' 23-21 win at the Suncorp Stadium but that charge was not upheld.
In handing down his decision, Judicial Officer, Nigel Hampton QC found that on the balance of probabilities he could not find an intentional or deliberate action of stamping or trampling.
"After hearing all the evidence I could not find that when James Horwill's right foot came into glancing contact with Alun Wyn Jones' face, that he Horwill was acting recklessly," said Mr Hampton, the same judicial officer who was brought into play earlier on in the tour when Lions prop Cian Healy was cleared of an alleged bite on Force scrum-half Brett Sheehan.
"I found that I could not reject as being implausible or improbable Horwill's explanation that as he was driving forward with his right leg raised he was spun off balance through the impact of Lions players entering the ruck from the opposite side.
"In an endeavour to regain his balance Horwill brought his right leg to the ground unknowing that Alun Wyn Jones' head was in that area, due to having his sight impeded by the presence of Michael Hooper and Tom Croft who were beneath him and over the top of Alun Wyn Jones. Due to these reasons I cannot uphold the citing."
Earlier in the day Lions head coach Warren Gatland explained why they had asked the citing officer to look into the incident in which lock Jones was caught by Horwill's boot at a ruck in the early exchanges.
"The medical team had a look at him at half-time. At full time they had to put a couple of stitches into his eye. We had a look at it after the game and the feeling from us was that it needed to be referred for the citing officer to have a look and for him to make his decision," said Gatland.
"I played in the days when rucking was allowed and I've still got some scars to bear witness to some of the decent ruckings I had. But the head for me was sacrosanct in terms of you stayed away from that."