How much available memory do you have on your phone? Sounds like the emails got deleted - or at least the attachments did.
"Forever" is not forever. It's more like "until your available memory get so low the blackberry is in danger of not being able to function". Check John Clark's excellent post on the subject for ways to reduce your memory use. For documents, I'd suggest getting a transflash card (micro SD) and saving the docs there where they will be safe. http://www.blackberryforums.com/gene...ee-memory.html