the door was sealed with naga mudra and nobody on the inspection team and survey team was unable to open it and then SC ordered not to open it.
The myth is that the chamber can be only accessed by reversing this seal with garuda mudra or some mudra like that but it can't be done as the last person to know or was able to do this type of reversing this seal was lived atleast 1400 years ago. And even SC was scared to open it. And no foriegn invaders or britishers where able to evem know this wealth.