A lip reader was used by the FA to determine what Mourinho said, reportedly a phrase in Portuguese, but they were unable to prove the charge.
However, ‘BBC Sport’ understands that Manchester United produced a strong defense for their manager and they feel vindicated by the outcome of the case.
The FA is surprised by the outcome and has not ruled out an appeal.
A statement from the association read: “A charge against Jose Mourinho for allegedly using language which was abusive and/or insulting and/or improper has been found not proven following an independent regulatory commission hearing.
“Written reasons for the decision of the independent regulatory commission will be published in due course. This decision is subject to appeal.”