PR 5 but no Backlinks?

I just bought a domain that has a PR 5, it wouldn't let me check to see if there where any back links because the domain just expired.

However I bought this because I assumed because it is a PR 5 which I was able to check that it would have back links but it doesn't?
I'm really confused why it doesn't have any backlinks but is ranked pr5.

Please fill me in.