i am sooo sorry for your loss
i dont know what the right answer is to the testing for ls or mvd, i know for me i will test any futrue yorkies i get between the ages of 6 months to 1 year depending on weight ect..... only because i want to know asap if i need to change their diet. having a dog with mvd i am so thankful to know we caught it before she was a year old so her liver wouldnt be damaged anymore. i do not think the testing should be the breeders responsibility to do before they leave their first home. a refund cost could maybe go back to the new parents to help cover the large bills. i know i would never want to replace lacey with a different dog she is a part of our family but even half back on her would have helped us out.