I updated to new iTunes 12.2.1.16 and my playlists are all gone. Is it possible to go back?

I keep my iTunes media files on an external drive so as to save space on my laptop. I have a lot of files. Because of my intermittent access to internet the iCloud isn't really useful to me.

When I started up the new iTunes my external drive was not mounted. Big mistake. iTunes created a new set of prefs and erased all my playlists and everything. I mounted the drive and set the iTunes media folder there as my default but iTunes still did not recognize or re-connect with my old prefs. They're probably gone. I had a decades worth of playlists there.

I put the freshest prefs in the trash and tried starting from scratch again, this time with the external drive mounted. But no dice. It's too late, isn't it?

Any suggestions?