Hashemtahir wrote:… how can they jst disappear like that !!
When you identify a picture as "Hidden," the picture carries a "hidden" mark. Then, wherever a picture is, if it has this hidden mark, then it's not shown on the screen. It isn't removed from the Library or removed from an album, it's just marked to not be shown. The "Hidden" view in Utilities shows every picture with the "hidden" mark.
Your "Hidden" view says that no pictures in your Library carry the "hidden" mark. If a picture is deleted, it won't have the hidden mark, so you should look in Recently Deleted. If they were deleted from there, then they are gone. Otherwise the pictures should appear in the same places they were before you marked them as "Hidden."
If you know the dates, you may be able to find the pictures by sorting the Library by "date captured" and looking among other pictures with similar dates. You can also search by date, location, objects, etc.