India Post — My urgent documents lost by Indian Post

Dear Sir

My Relative despatch a important documents through speed post vide docket no FS[protected]IN on dated 28.03.23 from Kotdwar Uttrakhand to Delhi but We have not received the same till date. We have register a complaint to AP to TMO post office vide complaint No [protected] on dated 31.05.23 and I have received response from AP to TMO on dated 04.07.2023 that my document has lost by Indian Postal Department. and finally I have lost my urgent documents

Sir Who is responsible for that, I want justice please help me