You are correct. The only way of knowing which cat the images were in is to have the old database. in there you would have the image filename and the catid, which is the Id of the category its in.
(and I am not sure how old versions of gallery handled that, because i dont have them any more and even couldnt install them as they dont support php5)
Originally Posted by Dr.H
It looks like the sub categories are just for displaying inside of vbgallery and all of the members files are still lumped together in their one gallery file folder on the server.
Unless you have safe mode on, the files should be in a directory for each user.
if safe mode is on then only they would be stray in the files folder, but each file would have the userid in front (example: user id 234 would have all image files starting with 234_ so example: 234_image.jpg)