lost documents by home office

i was granted a psw last week and my residence permit card arrived as well. however i am yet to receive my passport (with the new visa stamp) and other supporting documents (degree, transcripts etc). i had sent a pre paid special delivery envelope (next day guaranteed) along with my application. the home office claims that they have sent back my docs more than a week back but the royal mail does not have any record of my documents ( when i give them the tracking no)
i am very worried as i dont know where ,my docs are and who is liable, the home office says they cannot consider my passport as lost untill the 2nd of feb, but i had made provision for next day delivery so shouldnt it be considered missing right away. and the royal mail cant do anything as they dont have the parcel on their system and need the home office to make a formal complaint.
my issue is that if my passport is missing do i need to report it stolen to the police asap and apply for a new one at the indian consulate? and how to i make the home office or royal mail accountable for this fiasco?? please help... thanks