By "page authority" do you mean page rank? if so, those are faked on a massive scale. If you're looking to buy a domain, do it because you need it, not because it shows high page rank. To many people get scammed by chasing high page rank domains.

Use the wayback maschine (was that the name?) to check if the site got redirected in the past

Did you get the page authority directly from Moz or a third party tool?

Verify the page authority first using Open Site Explorer (moz.com/researchtools/ose)

If the page authority is correct and you entered the www version of the website, enter the non-www version of the website and you'll see all the backlinks to it.

Conversely, if the non-www version doesn't show any backlinks, enter the www version and you'll see the backlinks you couldn't find.

Hope this helps.

if they have zero backlinks that page authority or page rank will soon disappear

Concentrate on more important aspects of setting up a business as opposed to finding a domain with some juice on it