Sometimes petowners are a bit overwhelmed when coming back from a trip (catch up on bills, mountains of laundry etc.) and just haven’t had time to do the review. I think, unless you got some strange vibes from them, it’s perfectly fine to contact them and ask for a review. Mention how important it is to have good reviews as a sitter, and that if there were any problems you’d love to know about them so that you can avoid the issue on any future sits. For now, don’t overthink it. I’m sure you did a great job.