Were Ausralian  aboriginals completely isolated?
Tantalising evidence of  ancient Egyptian visitors to Australia is on this  Crystal links website. I personally had a friend who has visited a half excavated rock tomb at Gosford.,NSW Solid rock excavation is not done by aboriginals.
This page continues to list historic anomalies in the US such as roman swords found in California.
Crystal links
Masons greetings at the end of the above reference