Vinted complaint: Missing item but no ref

Hi
I have not recieved an order bought through Vinted , I had contact with seller for weeks as I was waiting for it .I was on away and missed the email sent by Vinted and I missed the 48hr response time to raise an issue . I have been in contact with Vinted and have asked numerous times for a manager to contact me but no response and no contact from a a manger and customer service have just said there is no more they can do and my claim is closed . The coat I bought is for my son to wear to school , I have had to buy another for him from Vinted but I can not afford to be out of pocket . I think it is very bad of Vinted to not help when I missed the cut of time by about 40 mins and to not have any flexibility at all . Please could someone get back to me as I really need my money back for the coat and I paid for and clearly did not receive.