Trying to add .vmdk file to inventory, but cannot see file

I am trying to add a .vmdk file someone gave me to my inventory.  I have already uploaded the VM folder containing the .vmdk file into my datastore.  Now, I want to have it in my inventory.  I tried adding a new VM, going to the custom configuration, and then when I reach "Select a disk", I pick the "Use an existing virtual disk".  I browse into my Datastore and see the VM folder, but inside there is nothing! No .vmdk file is there, but I know it IS when I just browse the datastore from the summary tab.  What is going on?  Thanks.