Unfortunately, it sounds like you may have missed your opportunity. If the game is still on sale, you may be able to purchase it again and gift it to your friend. However, it's unlikely that you will be able to unlock the pre-requisite amount again. Another option is to check if the game has any downloadable content (DLC) that you can gift. This way, your friend will still be able to benefit from the sale even though they already own the game.