But then the statue of Nokris wouldn't be there. The statue alone almost completely debunks the "erased from time" theory

Being erased from time doesn't necessarily mean destroy everything that had to do with them. If the statue was built while he existed, then he was erased, they would look at it and say "wait, who is this? Which is also why ghost had no info on him, no one remembers him. I think that's what that would imply but not really sure :P

The problem here is that the statue is solid evidence. Since the Books of Sorrow are also solid records, if the statue remains then so would any mention of Nokris in the Books Plus it's unlikely that our Ghost would be able to know the name of the Hive on the statue if Nokris was erased because the Ghost had to get the name from somewhere. The name Nokris was probably in the World's Grave library, allowing our Ghost to identify the statue, but there clearly was no other mention aside from the name