My bad, it should be in Documents/RenPy_Saves/com.dumbkoala.rebeccas if it manages to get to it. Also, did you get a file access request on the first launch?
I assume no files under that path? Thanks, I'll do some testing tomorrow and will probably do a new build with a potential fix. If you can only play on mobile right now, you can try using a PC version on mobile via JoiPlay.