Does the Quran or any hadith say that the Wall of Gog and Magog can't be seen by the human eye?

> Bring me **ingots of iron**." Then after he had filled up the space between the two mountain-sides, he said: "(Light a fire) and ply bellows." When he had made it (red like) fire, he said: "Bring me **molten copper** which I may pour on it." Surah 18 verse 96 It seems to me that the wall or barrier is physical as it uses materials such as iron. They're have been reports of historians claiming to see a wall, but no real hard evidence to back it up. Its 2018 and this brings to me my question, is there a reason as to why muslims and the rest of the human race can't find this wall? Did the Quran or any haidth ever say anything about the wall being invisible to the human eye? The question is a bit werid imo, so if you need clarification, just ask. May Allah forgive me for any mistakes.