Where did Mainstage 3 Sound library go?

I have been using Mainstage 3 for months now with no problems. This afternoon I was playing sounds on it just fine. I packed it up to go to rehearsal and when I got there and opened Mainstage, I get the "Thank you for purchasing and downloading Mainstage from the Mac App Store" message, and it starts downloading the sound library again.

I was logged in as me (the only user other than the admin). I tried logging out and back in, then rebooting and logging in. Either way, when Mainstage was opened, it started downloading the sound library again. I do not use an external drive, so I don't think that is the problem.

It's not a big deal to just download them again, but it's weird that they are gone.

There was no option to open Mainstage and browse to the folder where the sounds are, it just downloads them again.

Any thoughts?