Was this ever solved?
I did an import from vB 3.8.1 to XF 2. So far, most everything worked as expected. During the import, I was asked to provide a path to the attachment files and I gave that after verifying it was correct. However, all of my threads that had attachments in vB now have nothing, not even a bad link to a missing attachment. It is like that info was just stripped out of the posts.
If I go to Admin CP -> Content -> Attachments, the attachment browser shows "no results found." However, if I look here /public_html/forums/data/attachments/, there are loads of images. So it looks like XF made copies, but then doesn't do anything with them.