Ruffle Trim Short Sleeve Sweater

I really loved this sweater and I only wore once and it got shrank after one wash ( not the dryer ) We have a front load type 5 years old washing machine. I'm always careful washing the knit sweaters. I turned the sweater inside out and put it in a laundry net, and used a delicate detergent and softener with cold water and used delicate cycle. All my knit sweaters and other items were fine, but this sweater became from L size to 10 years old shirts ( almost same size as my kid's shirts). I really don't know why! I hope they would accept return.