The only thing that I can think of to explain this would maybe be if you did not mark the dead stones/prisoners, or your opponent marked live stones dead which gave him a lead. If you have the sgf I or someone else could explain to you what happened, but without the record its really all speculation. You say you had 146 prisoners, was that actually captured stones (already removed from the board) or dead stones? If they were actually captured than the only way I can figure you to have lost is if your opponent marked live stones dead...