Unfortunately, to an extent, the account in question was in fact boosted and utilized unauthorized third-party applications to do so. Whether or not the intent was there to create a negative competitive environment for other players, that's what in essence happened by either allowing a booster to use your account or not reporting such an instance to Riot and taking active measures to ensure that you're the only one with access to your account.
As such, I don't see any situation in which Riot will be reversing this suspension, as iterated by Riot Support's response in the ticket that the matter is closed. If you have any questions, please let me know.
Additional read: http://boards.na.leagueoflegends.com/en/c/player-behavior-moderation/yrqwIqfF-psa-dont-participate-in-mmr-boosting