This happens sometimes at our site as well.
But the problem is that you make a save as and then sometimes (mostly if you do many save as-operations) the EPDM doesn't add the file to the vault properly.
But normaly the user which creates the can add this to the vault. In the options you can give the user acces to all Files not only the one which where added to the vault.
Does the file card for the assembly show up? It might be that the card does not have the sldasm extension associated with it.
Yes the Assembly would have a working file card