audiobooks disappear in iTunes

I put audiobooks from the 'Audiobook' folder in Itunes on computer A onto my ipod. I can listen to it fine on my ipod - I found it under Music > Audiobooks. However, when I plug the ipod into computer B, there is no 'Audiobooks' folder either in my main library or in the Device/ipod listing. It's not in music either - these audiobooks seemed to have completely disappeared. This is in iTunes 7.

Many people write in saying they want to switch the placement of their audiobook from 'Music' to 'Audiobooks', but I can't even find where these files are to listen to or convert the files.