It is as they say: the best laid plans can often go awry. Even the most heavily tested builds of iOS — ones that many thousands of iOS developers Beta tested, and ones that had multiple last minute Gold Master revisions — can have surprise bugs lurking when things go live.

Such is the case with iOS 4.2, which has at least one strange bug in its bed. Upon updating to the just released software, a solid number of users are reporting that their music library has gone missing. Fear not, music lovers! There’s an easy fix.

Turns out, your music isn’t gone. It’s just hiding.

How to get it back:

1. Connect your iOS device to iTunes over USB
2. iTunes will show your iOS device’s music library. Pick any song from your iOS device, play it through iTunes.
3. Now that the play count has changed, the Sync button can be clicked. Click the Sync button.
4. Open the iPod application on the iOS device. It’ll rebuild your music library, and you’ll be gettin’ all Fergilicious in no time.

Shout out to AppleZilla on the Apple forums for figuring out this quick fix, and Jeremy for bringing it to our attention. s