Daily Chinese Idiom Guessing Game
To look at something but not see it; to ignore or disregard something obvious.
指不注意，不重视，睁着眼却没看见。也指不理睬，看见了当作没看见。
《礼记·大学》心不在焉，视而不见，听而不闻，食而不知其味。”
He was so absorbed in his phone that he was totally oblivious to his friend waving at him.