My girlfriend purchased some albums using the iTunes store from within her iPod touch. Sadly, she connected the iPod touch to iTunes and now the albums are gone. I have no idea what happened, maybe some sync/backup problem. Is it possible to recover those albums? Why does iTunes decides to delete purchased songs?
When you buy a song, video, iPod Game, or album from the iTunes Store, you are entitled to download it only once.
Is the purchased content still on the iPod? If so, you can just right click the iPod in iTunes and select "Transfer purchases".
Alternatively, you could try going to the Store menu in iTunes, then Check for available downloads. It's a long shot, but it might just work.
Apart from that, you don't really have any other option, apart from contacting Apple, plead your case, and just hope that they would be able to let you re-download your lost music.
The moral to this story? Once again, Apple chimes in:
Make a backup of the content you purchase. In case of data loss, including hard drive failure or replacement, accidental deletion, and so forth, you'll be able to restore it from the backup. See How to back up your media in iTunes for instructions.