You are not missing any folders, there are no folders numbered: 038, 039 and 044-089.

001-099 is just describing the range between the first and last folder. Some folder numbers has been skipped to make the collection more organized. For example the Doodles Stamps are located in folders 31-37 and then it starts with Backgrounds on 40. We made it this way to make it easier to find your stamps fast.

Don't forget to register your copy to get more bonus stamps:
http://go.softwarecasa.com/superstamps-registration/