Nautilus doesn't recognise directories for unknown users

Binary package hint: nautilus

Ubuntu 8.10
Nautilus: 1:2.24.1-0ubuntu2

I backed up my /home directory (containing a no. of users) to an external USB hard drive using grsync (preserving owner). Due to an imminent failure on my internal hard drive, I re-installed Ubuntu onto a new hard disk. When I attached the external hard drive, nautilus indicated that whilst there was 60Gb of data upon inspection of the directories these proved empty with size being indicated by ? items.

This seemed to occur because the users had not been created, and hence nautilus could not make sense of the directory structure. Using the command 'ls -lR' clearly indicated that the directory structure was intact. For unknown users, the ownership was given as a four digit number.

I expect Nautilus to be able to accurately provide information on the directory structure even if the users are unknown.

This could be seen as a security vulnerability because a user may consider that their file system is corrupt and believe that reformatting the hard drive would regain the disk space (in my case 60Gb)