(iOS) How to retrieve the player's current score on a specific leaderboard

I am looking for a way to simply retrieve the player's current score for a given leaderboard, without having to go through all the other scores which I am not interested in.

The reason I need this, is to compare the current score (what is shown on the leaderboard) to what the player's actual score is (stored locally), so that they always remain in sync.

By the way, the Social API, as it is currently implemented, is an embarrassment to Unity. For example, the callbacks from ReportScore and ReportProgress are completely useless, as they always return successful even when the user is offline. This problem has been ongoing since 2012.