Hard to tell as no information was provided on your website.
But if it was ranking for a year, and suddenly vanished, chances are, your link profile could have changed - meaning if you purchased links in the past, these links could have been demoted all of a sudden, and with the power links now demoted to useless links, your site doesn't rank anymore in the process.
The only good links and sustainable ones are from extremely hq news sites or equivalent, and those would allow your site to rank in a stable manner - but even authority sites' ranking would fluctuate every now and then.