How can an unmarried woman get married while adhering to the شرعي حجاب, especially since no one has seen her? And does the story of the man who hid to see the girl indicate her lack of حجاب?

There is no disagreement regarding the obligation of the legal hijab, but scholars have differed on the obligation of covering the face and hands. Islamic law has permitted a suitor to look at his fiancée, and if he is unable to do so, he may send a woman to look at her and describe her to him, as the Prophet, peace and blessings be upon him, did when he sent Umm Sulaym to a woman. The story mentioned does not indicate that the woman was uncovering her face; rather, it appears that she was covering it, which is why he needed to hide to see her. If her face had been uncovered, he would not have needed to do so. A woman covering her face does not reduce her chances of marriage; in fact, reality shows that the chances of marriage are higher for women who are committed to covering their faces.