Everytime anyone purchases through Etsy, at the very top of the page on the left side, there will be a reminder (after the date the item should have shipped to them), the reminder will be something like, "you have an item ready to review).
I honestly don't think the average buyer spends nearly as much time on Etsy as us shop owners do, so they may not even notice it.
Since I run 2 businesses, one on Etsy, one in my interior design business, I feel really confident that if someone was unhappy you would certainly hear about it.