I've noticed some strange things in VMWare.
Most of my VM's have more than 1 disk. For example, Exchange VM has a disk for OS, a disk for Logs and a disk for Mailboxes.
Physcially, these represent different targets on my iSCSI SAN, which reside on different speed/capacity arrays.
In the VM Summary View, some VM's show only the OS datastore connected, However, if you go to Edit Settings, you can see the other disks on the other Datastores connected, If you go into Datastore view you can also select the Datastore and it shows its connected to the VM there.