Bit pissed right now the game asked me to rate it and offered an ingame reward but after it opened the browser and I wrote my review my phone stopped the app and I lost like 2h of progress because I forgot to save frequently. Maybe consider implementing autosave for promts like that to prevent frustrations like mine. Gotta say otherwise a real fun and charming game though.
So sorry to hear that happened to you. Check to see if it did autosave as renpy already does so, autosaves should be under the 'A' section of the load screen, hopefully it had saved then.
We've already implemented that for future versions, adding multiple forced autosaves, reminders, and even forcing players to hard save every in-game week and before that prompt shows up.