It's capable of choosing its wielder. I had it before I found out what it was even called and didn't even have time to question it until I got to another world. And most of my information for a while was bits and pieces from people who only knew bits and pieces.

[In a nutshell, he didn't actually have a master until he met Yen Sid, which he's already mentioned to Eraqus.]

Lea and Wash were there.