If we're going to get technical, just because there is no proof that any of that happened that does not mean that it didn't, correct? Some of it is more far fetched then others of course... If a country or group of people where going to hid something of value you wouldn't let everyone in on it would you? Only a choice few people would have known about it and maybe they did write about it and it either got destroyed in transit or just has never been found for others to read about it...
Just because it has never been read some where that any of that did happen, doesn't mean that it didn't, and just because something is in writing doesn't make it fact..
Just because it has never been read some where that any of that did happen, doesn't mean that it didn't, and just because something is in writing doesn't make it fact..