student finance has lost my passport?

student finance asked me to send off passport.
i send it off with tracked delivery costing me £9.
its been 4 weeks and still not got it back.
i call them last week asking for it and they said they'll send it the next day with tracked next day delivery.
it has been a week and still no passport, i dont think they sent it.
have they lost my passport? would they lie about it? im going to have to call them again tomorrow asking for it but its just frustrating me to no ends now why they just refuse to give me back my passport while i have 2 holidays coming up so i NEED it back