Thanks so much for your feedback and I'm glad you've enjoyed it!
We're investigating Geists being deleted like you mentioned. Did you use a move during battle, and they disappeared after?
Really sorry to hear that! This looks like a bug we're investigating for a patch coming really soon.
If you saved, you should be able to re-encounter Keroking. If you didnt save but want to continue and experience the rest of Case 1 with the team you had, email me at photogeist.dev@gmail.com and I'll get you set back up!