There is a way, but I would make a library backup first.
You can sort the view of your media by filename.
Select all that belong on the drive in question.
As an example, say you are only interested in checking your video files, and they are all in: E:\Media\Movies\
Use Rename, Move and Copy files to move all of the files that are in your library to:
E:\media\Movies\Test\ <- Test is a new directory you are making and moving everything that is in your MC library into temporarily. You will use MC to do the move.
Do this by ONLY using the Find/Replace function in the default Rename (move files if directory changes) mode.
Find: E:\Media\Movies\
replace with: E:\media\Movies\Test\
If all your movie files are imported into MC, everything that was in E:\media\Movies\ will be moved to E:\media\Movies\Test\
You can then move it all back in one step by doing the opposite find and replace.
Anything that was not imported into MC will remain behind in E:\media\Movies\
You'd have to repeat this kind of thing for each media subtype you have in MC.
This is not elegant.
It is a little risky if you don't know what you're doing.
But it works if you have a large library.
There should be other ways that might be simpler.
