From the tone of voice, the other party seemed to know its origin; however, the phantom of the Green Lotus merely considered this an illusion and didn't believe that the man in front of it truly knew.
For one, the events of that year were too ancient and although not as untraceable as the Emperor Fallen era, it spanned a major epoch and was separated by quite a few smaller eras.
The people only knew the outcome of that battle but not the specifics.
Secondly, it was the most intense period of the Ancient Immortal War.
The Primitive Ancient Realm shattered and corpses lay everywhere. Fire of war raged across the landscape and everyone fought for themselves. Even the Supremes were besieged by a horde of Immortal Beings from the Alien Territory.
Not to mention the Immortals, who fell in droves; everyone was too busy looking after themselves...
Therefore, apart from itself, it was impossible for anyone else to know its true identity.