Lost library after external drive disconnected

HI, yesterday I had to disconnect my external drive where I keep my Calibre library, in order to use another drive.

While I was using the other drive I accidentally opened Calibre.

Now, my Calibre library is empty and I can't seem to restore it. It's changed the file path for the folder, but changing it back isn't working.

Can anyone advise what to do? Thank you in advance!