I'm thoroughly confused but it sounds like you purchased an expired domain. A site that is offline isn't going to maintain PR for long so I wouldn't base that as a reason to buy unless the site was still online. PR is updated constantly but only reflected periodically in the toolbar. It probably had no PR but the purchase coincided in the toolbar update. I just had a page go from 0 to 3 a couple days ago (at least that's when I noticed). Suggest getting some original content up fast. You'll probably have to wait for the next update to notice any changes in PR. Good luck