i believe there is multiple master swords not one.
evidence: in skyward sword it claims the goddess made the sword but in a link to the past (aka triforce of the gods) it is claimed that the six sages forged the blade (at least the manga said so). there are many variations of the sword including the dark master sword all have slight difference in design
"i believed this before i had any evidence, it was also a idea i had for a movie"
Interesting. As another posted on here, perhaps the sword was re-forged by those sages. And while being re-forged, there may have been a duplicate made for all we know. That Master Sword is one mysterious weapon.