Or, how about:
"Thanks so much for creating this game that I've obviously liked enough to play multiple times! Happened to notice my stats weren't saving, any plans to update? Appreciate the time you've put into providing us with this game either way."
Anyone who complains about a free game not getting extra features needs to ask themselves how they'd feel if they'd volunteered somewhere, or donated items or money, and someone came back and complained that it wasn't good enough, and why weren't they doing more? r/choosingbeggars
Sorry, but this really frosts my cookies.