After the save as, you got an NWD called 14_0626...Model.NWD.
You can Append NWD's to an nwf, in your case the Test.NWF, just like any other supported filetype.
Quit Navisworks and use the explorer to look at the files.
When you used "save as", you should still have your original Master nwf file, but then without the changes. Just dubbleclick it and remake the changes that you must make.
Depending on what the changes are, you could export viewpoints, selection sets etc from the NWD and then import them into the NWF.
OR, you could open the NWF, MERGE the NWD also to the NWF to import the changes. Then Delete the NWD from the selection tree,