I'm assuming the site files are stored localy as well as on your server? If so- link to the folders that the content is in. If not- find out the ftp, and download them so you have a local copy. As for re-inserting your ftp information- if you don't know what it is- then hopefully you can recover the information by emailing tripod.
Why it's done this- I have no idea, unless you have re-installed Dreamweaver, your files shouldn't dissapear- have you checked your machine for viruses lately? Sometimes, when my code just won't behave, I take it outside and make it listen to britney spears music, and when it comes back it's really well behaved. I wonder if it's suffering from post tramatic stress syndrome now..