Not sure if this is a rhetorical question, but I'm a total geek and an IT professional, so I can't resist answering, in two ways:
1) It's really easy for a system to end up apparently losing registrations. There's a database that stores all the info in the system, and the fields which are storing the registration info are all very much intact. But for whatever reason, the pages designed to call up that registration and allow you to view/edit it aren't working properly. Maybe it's a web design issue. Maybe it's something wrong with the query which searches for the registration. But this happens all the time when we're developing and testing new systems. It's just that we're supposed to find these issues and fix them in the development/test systems before the systems are actually being used for their intended purpose.
2) It's completely ludicrous and unnecessary that Disney is (apparently) losing registrations. There's no reason for this to happen if they'd just follow good practices for software development and ongoing support. And my guess is they don't have adequate quality assurance practices.