Data Loss

I recently installed Lucid on my desktop, without formatting my home directory, which is what I normally do for each release.

This time, however, all the files in my Ubuntu One folder had vanished without a trace. I'm thinking there might have been an error when updating for the first time on a fresh install.
It's my fault that there are no backups, but I was wondering what kind of procedure is required to recover the files from a couple of weeks ago (about 3-4), if it's at all possible?

Thank you for your help,

Adam