This may happen in two variants: either because at the end of the match the game was not refreshed so there might be a visual glitch, or because your opponent was challenging another player and won at the similar time he lost a trophy against you.
What you should also have in mind is that in case it was the first duel you had, a trophy won’t be deducted from the losing side, since that Manager already had none.
King of Kings: I won against other Manager but his trophy was not taken
Last Updated: 2d